CLEANUP: haproxy: Remove unused variable

Looking at the code, this variable is no longer used and referenced
nowhere. That means it can be safely removed.
diff --git a/src/haproxy.c b/src/haproxy.c
index 728e71d..febef26 100644
--- a/src/haproxy.c
+++ b/src/haproxy.c
@@ -204,7 +204,6 @@
 
 int *children = NULL; /* store PIDs of children in master workers mode */
 
-static volatile sig_atomic_t caught_signal = 0;
 static char **next_argv = NULL;
 
 struct list proc_list = LIST_HEAD_INIT(proc_list);