[AUDIT] add session id to audit messages

In order to correlate audit records to an individual login add a session
id.  This is incremented every time a user logs in and is included in
almost all messages which currently output the auid.  The field is
labeled ses=  or oses=

Signed-off-by: Eric Paris <eparis@redhat.com>

include/linux/init_task.h

@@ -116,7 +116,8 @@ extern struct group_info init_groups;
 
 #ifdef CONFIG_AUDITSYSCALL
 #define INIT_IDS \
-	.loginuid = -1,
+	.loginuid = -1, \
+	.sessionid = -1,
 #else
 #define INIT_IDS
 #endif