MINOR: activity: rename the "stream" field to "stream_calls"

This one was confusingly called, I thought it was the cumulated number
of streams but it's the number of calls to process_stream(). Let's make
this clearer.
diff --git a/include/haproxy/activity-t.h b/include/haproxy/activity-t.h
index 77840dc..6fc5844 100644
--- a/include/haproxy/activity-t.h
+++ b/include/haproxy/activity-t.h
@@ -46,7 +46,7 @@
 	unsigned int poll_dead_fd; // poller woke up with a dead FD
 	unsigned int poll_skip_fd; // poller skipped another thread's FD
 	unsigned int conn_dead;    // conn_fd_handler woke up on an FD indicating a dead connection
-	unsigned int stream;       // calls to process_stream()
+	unsigned int stream_calls; // calls to process_stream()
 	unsigned int ctxsw;        // total number of context switches
 	unsigned int tasksw;       // total number of task switches
 	unsigned int empty_rq;     // calls to process_runnable_tasks() with nothing for the thread
diff --git a/src/cli.c b/src/cli.c
index cbc6136..12dc8e6 100644
--- a/src/cli.c
+++ b/src/cli.c
@@ -1139,7 +1139,7 @@
 	chunk_appendf(&trash, "poll_dead_fd:"); SHOW_TOT(thr, activity[thr].poll_dead_fd);
 	chunk_appendf(&trash, "poll_skip_fd:"); SHOW_TOT(thr, activity[thr].poll_skip_fd);
 	chunk_appendf(&trash, "conn_dead:");    SHOW_TOT(thr, activity[thr].conn_dead);
-	chunk_appendf(&trash, "stream:");       SHOW_TOT(thr, activity[thr].stream);
+	chunk_appendf(&trash, "stream_calls:"); SHOW_TOT(thr, activity[thr].stream_calls);
 	chunk_appendf(&trash, "pool_fail:");    SHOW_TOT(thr, activity[thr].pool_fail);
 	chunk_appendf(&trash, "buf_wait:");     SHOW_TOT(thr, activity[thr].buf_wait);
 	chunk_appendf(&trash, "cpust_ms_tot:"); SHOW_TOT(thr, activity[thr].cpust_total / 2);
diff --git a/src/stream.c b/src/stream.c
index 0c02cfb..f0618de 100644
--- a/src/stream.c
+++ b/src/stream.c
@@ -1495,7 +1495,7 @@
 
 	DBG_TRACE_ENTER(STRM_EV_STRM_PROC, s);
 
-	activity[tid].stream++;
+	activity[tid].stream_calls++;
 
 	req = &s->req;
 	res = &s->res;