api: Set errno before invoking glfs_init_done()

Change-Id: I3f4d3cfaf7078e126881111eb840d854b0b6466d
BUG: 860212
Signed-off-by: Vijay Bellur <vbellur@redhat.com>
Reviewed-on: http://review.gluster.org/5704
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Anand Avati <avati@redhat.com>