IB/srp: Remove an extraneous scsi_host_put() from an error path

Fix a scsi_get_host() / scsi_host_put() imbalance in the error
path of srp_create_target(). See also patch "IB/srp: Avoid that
I/O hangs due to a cable pull during LUN scanning" (commit ID
34aa654e

).

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Reviewed-by: Sagi Grimberg <sagig@mellanox.com>
Cc: Sebastian Parschauer <sebastian.riemer@profitbricks.com>
Cc: <stable@vger.kernel.org> #v3.19
Signed-off-by: Doug Ledford <dledford@redhat.com>