MINOR: counters: factor out smp_fetch_sc*_tracked

The new function makes use of the sc# in the keyword to
get the counter ID.
diff --git a/src/session.c b/src/session.c
index 2fc2dcb..aa42c31 100644
--- a/src/session.c
+++ b/src/session.c
@@ -2578,36 +2578,17 @@
 /*           All supported ACL keywords must be declared here.          */
 /************************************************************************/
 
-/* set return a boolean indicating if sc0 is currently being tracked or not */
-static int
-smp_fetch_sc0_tracked(struct proxy *px, struct session *l4, void *l7, unsigned int opt,
-                      const struct arg *args, struct sample *smp, const char *kw)
-{
-	smp->flags = SMP_F_VOL_TEST;
-	smp->type = SMP_T_BOOL;
-	smp->data.uint = !!l4->stkctr[0].entry;
-	return 1;
-}
-
-/* set return a boolean indicating if sc1 is currently being tracked or not */
-static int
-smp_fetch_sc1_tracked(struct proxy *px, struct session *l4, void *l7, unsigned int opt,
-                      const struct arg *args, struct sample *smp, const char *kw)
-{
-	smp->flags = SMP_F_VOL_TEST;
-	smp->type = SMP_T_BOOL;
-	smp->data.uint = !!l4->stkctr[1].entry;
-	return 1;
-}
-
-/* set return a boolean indicating if sc2 is currently being tracked or not */
+/* set return a boolean indicating if the requested session counter is
+ * currently being tracked or not.
+ * Supports being called as "sc[0-9]_tracked" only.
+ */
 static int
-smp_fetch_sc2_tracked(struct proxy *px, struct session *l4, void *l7, unsigned int opt,
+smp_fetch_sc_tracked(struct proxy *px, struct session *l4, void *l7, unsigned int opt,
                       const struct arg *args, struct sample *smp, const char *kw)
 {
 	smp->flags = SMP_F_VOL_TEST;
 	smp->type = SMP_T_BOOL;
-	smp->data.uint = !!l4->stkctr[2].entry;
+	smp->data.uint = !!l4->stkctr[kw[2] - '0'].entry;
 	return 1;
 }
 
@@ -3961,7 +3942,7 @@
 	{ "sc0_kbytes_out",     smp_fetch_sc0_kbytes_out,     0,           NULL, SMP_T_UINT, SMP_USE_L4CLI, },
 	{ "sc0_sess_cnt",       smp_fetch_sc0_sess_cnt,       0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
 	{ "sc0_sess_rate",      smp_fetch_sc0_sess_rate,      0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
-	{ "sc0_tracked",        smp_fetch_sc0_tracked,        0,           NULL, SMP_T_BOOL, SMP_USE_INTRN, },
+	{ "sc0_tracked",        smp_fetch_sc_tracked,         0,           NULL, SMP_T_BOOL, SMP_USE_INTRN, },
 	{ "sc0_trackers",       smp_fetch_sc0_trackers,       0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
 	{ "sc1_bytes_in_rate",  smp_fetch_sc1_bytes_in_rate,  0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
 	{ "sc1_bytes_out_rate", smp_fetch_sc1_bytes_out_rate, 0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
@@ -3980,7 +3961,7 @@
 	{ "sc1_kbytes_out",     smp_fetch_sc1_kbytes_out,     0,           NULL, SMP_T_UINT, SMP_USE_L4CLI, },
 	{ "sc1_sess_cnt",       smp_fetch_sc1_sess_cnt,       0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
 	{ "sc1_sess_rate",      smp_fetch_sc1_sess_rate,      0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
-	{ "sc1_tracked",        smp_fetch_sc1_tracked,        0,           NULL, SMP_T_BOOL, SMP_USE_INTRN, },
+	{ "sc1_tracked",        smp_fetch_sc_tracked,         0,           NULL, SMP_T_BOOL, SMP_USE_INTRN, },
 	{ "sc1_trackers",       smp_fetch_sc1_trackers,       0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
 	{ "sc2_bytes_in_rate",  smp_fetch_sc2_bytes_in_rate,  0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
 	{ "sc2_bytes_out_rate", smp_fetch_sc2_bytes_out_rate, 0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
@@ -3999,7 +3980,7 @@
 	{ "sc2_kbytes_out",     smp_fetch_sc2_kbytes_out,     0,           NULL, SMP_T_UINT, SMP_USE_L4CLI, },
 	{ "sc2_sess_cnt",       smp_fetch_sc2_sess_cnt,       0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
 	{ "sc2_sess_rate",      smp_fetch_sc2_sess_rate,      0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
-	{ "sc2_tracked",        smp_fetch_sc2_tracked,        0,           NULL, SMP_T_BOOL, SMP_USE_INTRN, },
+	{ "sc2_tracked",        smp_fetch_sc_tracked,         0,           NULL, SMP_T_BOOL, SMP_USE_INTRN, },
 	{ "sc2_trackers",       smp_fetch_sc2_trackers,       0,           NULL, SMP_T_UINT, SMP_USE_INTRN, },
 	{ "src_bytes_in_rate",  smp_fetch_src_bytes_in_rate,  ARG1(1,TAB), NULL, SMP_T_UINT, SMP_USE_L4CLI, },
 	{ "src_bytes_out_rate", smp_fetch_src_bytes_out_rate, ARG1(1,TAB), NULL, SMP_T_UINT, SMP_USE_L4CLI, },