scm: improve serialization of destroy and state changes

scm: improve serialization of destroy and state changes

WinOF testing with slightly different scheduler and verbs
showed some issues with cleanup. Add better protection around
destroy and move state change before socket send to insure
correct state in multi-thread environment targeting the same
device on send and recv.

Change DCM_RTU_PENDING to DCM_REP_PENDING and
and add static definition to local routines for better
readability.

Signed-off-by: Arlin Davis <arlin.r.davis@intel.com>