MINOR: log: make log-format expressions completely usable outside of req/resp

The log-format strings are usable at plenty of places, but the expressions
using %[] were restricted to request or response context and nothing else.
This prevents from using them from the config context or the CLI, let's
relax this.
diff --git a/src/log.c b/src/log.c
index 1804062..5cae182 100644
--- a/src/log.c
+++ b/src/log.c
@@ -2075,8 +2075,13 @@
 				key = NULL;
 				if (tmp->options & LOG_OPT_REQ_CAP)
 					key = sample_fetch_as_type(be, sess, s, SMP_OPT_DIR_REQ|SMP_OPT_FINAL, tmp->expr, SMP_T_STR);
+
 				if (!key && (tmp->options & LOG_OPT_RES_CAP))
 					key = sample_fetch_as_type(be, sess, s, SMP_OPT_DIR_RES|SMP_OPT_FINAL, tmp->expr, SMP_T_STR);
+
+				if (!key && !(tmp->options & (LOG_OPT_REQ_CAP|LOG_OPT_RES_CAP))) // cfg, cli
+					key = sample_fetch_as_type(be, sess, s, SMP_OPT_FINAL, tmp->expr, SMP_T_STR);
+
 				if (tmp->options & LOG_OPT_HTTP)
 					ret = lf_encode_chunk(tmplog, dst + maxsize,
 					                      '%', http_encode_map, key ? &key->data.u.str : &empty, tmp);