NFS add a simple sync nfs4_proc_commit after async COPY

A COPY with unstable write data needs a simple sync commit.
Filehandle value is gotten as a part of the inner loop so in
case of a reboot retry it should get the new value.

Signed-off-by: Olga Kornievskaia <kolga@netapp.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>