Add tracepoints for reconnecting an smb3 session

Example output (from trace-cmd) with the patch
(showing the session marked for reconnect, the stat failing, and then
the subsequent SMB3 commands after the server comes back up).
The "smb3_reconnect" event is the new one.

           cifsd-25993 [000] .... 29635.368265: smb3_reconnect: server=localhost current_mid=0x1e
            stat-26200 [001] .... 29638.516403: smb3_enter: 	cifs_revalidate_dentry_attr: xid=22
            stat-26200 [001] .... 29648.723296: smb3_exit_err: 	cifs_revalidate_dentry_attr: xid=22 rc=-112
     kworker/0:1-22830 [000] .... 29653.850947: smb3_cmd_done: 	sid=0x0 tid=0x0 cmd=0 mid=0
     kworker/0:1-22830 [000] .... 29653.851191: smb3_cmd_err: 	sid=0x8ae4683c tid=0x0 cmd=1 mid=1 status=0xc0000016 rc=-5
     kworker/0:1-22830 [000] .... 29653.855254: smb3_cmd_done: 	sid=0x8ae4683c tid=0x0 cmd=1 mid=2
     kworker/0:1-22830 [000] .... 29653.855482: smb3_cmd_done: 	sid=0x8ae4683c tid=0x8084f30d cmd=3 mid=3
Signed-off-by: Steve French <stfrench@microsoft.com>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Reviewed-by: Aurelien Aptel <aaptel@suse.com>