scsi_dh_alua: Make stpg synchronous

scsi_dh_alua: Make stpg synchronous

The 'activate_complete' function needs to be executed after
stpg has finished, so we can as well execute stpg synchronously
and call the function directly.

Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
BugLink: http://bugs.launchpad.net/bugs/1567602
(cherry-picked from commit b2460756660c6a6d1be8e35a18521d5c2a3f5823)
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Brad Figg <brad.figg@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>