MINOR: mailers: increase default timeout to 10 seconds

This allows the tcp connection to send multiple SYN packets, so 1 lost
packet does not cause the mail to be lost. It changes the socket timeout
from 2 to 10 seconds, this allows for 3 syn packets to be send and
waiting a little for their reply.

This patch should be backported to 1.6.

Acked-by: Simon Horman <horms@verge.net.au>
diff --git a/include/common/defaults.h b/include/common/defaults.h
index d1994e8..1c971d9 100644
--- a/include/common/defaults.h
+++ b/include/common/defaults.h
@@ -146,6 +146,7 @@
 
 #define	CHK_CONNTIME    2000
 #define	DEF_CHKINTR     2000
+#define DEF_MAILALERTTIME 10000
 #define DEF_FALLTIME    3
 #define DEF_RISETIME    2
 #define DEF_AGENT_FALLTIME    1