BUG/MINOR: check: Wake the check task if the check is finished in wake_srv_chk()

With tcp-check, the result of the check is set by the function tcpcheck_main()
from the I/O layer. So it is important to wake up the check task to handle the
result and finish the check. Otherwise, we will wait the task timeout to handle
the result of a tcp-check, delaying the next check by as much.

This patch also fixes a problem about email alerts reported by PiBa-NL (Pieter)
on the ML [1] on all versions since the 1.6. So this patch must be backported
from 1.9 to 1.6.

[1] https://www.mail-archive.com/haproxy@formilux.org/msg32190.html
diff --git a/src/checks.c b/src/checks.c
index 1a81ccd..b0de770 100644
--- a/src/checks.c
+++ b/src/checks.c
@@ -1442,12 +1442,13 @@
 	}
 
 	if (check->result != CHK_RES_UNKNOWN) {
-		/* We're here because nobody wants to handle the error, so we
-		 * sure want to abort the hard way.
-		 */
+		/* Check complete or aborted. If connection not yet closed do it
+		 * now and wake the check task up to be sure the result is
+		 * handled ASAP. */
 		conn_sock_drain(conn);
 		cs_close(cs);
 		ret = -1;
+		task_wakeup(check->task, TASK_WOKEN_IO);
 	}
 
 	if (check->server)