CLEANUP: activity: remove unused counter fd_lock

Since 2.1-dev2, with commit 305d5ab46 ("MAJOR: fd: Get rid of the fd cache.")
we don't have the fd_lock anymore and as such its acitvity counter is always
zero. Let's remove it from the struct and from "show activity" output, as
there are already plenty of indicators to look at.

The cache line comment in the struct activity was updated to reflect
reality as it looks like another one already got removed in the past.
diff --git a/include/haproxy/activity-t.h b/include/haproxy/activity-t.h
index 3bc81b3..3020806 100644
--- a/include/haproxy/activity-t.h
+++ b/include/haproxy/activity-t.h
@@ -44,7 +44,6 @@
 	unsigned int poll_drop;    // poller dropped a dead FD from the update list
 	unsigned int poll_dead;    // poller woke up with a dead FD
 	unsigned int poll_skip;    // poller skipped another thread's FD
-	unsigned int fd_lock;      // fd cache skipped a locked 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 ctxsw;        // total number of context switches
@@ -52,7 +51,9 @@
 	unsigned int empty_rq;     // calls to process_runnable_tasks() with nothing for the thread
 	unsigned int long_rq;      // process_runnable_tasks() left with tasks in the run queue
 	unsigned int cpust_total;  // sum of half-ms stolen per thread
-	/* one cache line */
+	/* two unused entries left before end of first cache line */
+	ALWAYS_ALIGN(64);
+
 	struct freq_ctr cpust_1s;  // avg amount of half-ms stolen over last second
 	struct freq_ctr_period cpust_15s; // avg amount of half-ms stolen over last 15s
 	unsigned int avg_loop_us;  // average run time per loop over last 1024 runs
diff --git a/src/cli.c b/src/cli.c
index a8d3934..22fc771 100644
--- a/src/cli.c
+++ b/src/cli.c
@@ -1133,7 +1133,6 @@
 	chunk_appendf(&trash, "poll_drop:");    SHOW_TOT(thr, activity[thr].poll_drop);
 	chunk_appendf(&trash, "poll_dead:");    SHOW_TOT(thr, activity[thr].poll_dead);
 	chunk_appendf(&trash, "poll_skip:");    SHOW_TOT(thr, activity[thr].poll_skip);
-	chunk_appendf(&trash, "fd_lock:");      SHOW_TOT(thr, activity[thr].fd_lock);
 	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, "pool_fail:");    SHOW_TOT(thr, activity[thr].pool_fail);