OSHMEM: sshmem verbs: workaround shared_mr procfs bug

dereg shared_mr before doing dereg on its mr.
(cherry picked from commit cd67642183954d5dad560d907ded422d47ee50d4)
Merge pull request #20 from alex-mikheev/topic/oshmem_shared_mr_fix-v1.8

OSHMEM: sshmem verbs: workaround shared_mr procfs bug