LU-14534 gss: do not refresh context for LDLM callback

LU-14534 gss: do not refresh context for LDLM callback

If the request to be sent is an LDLM callback, do not try to
refresh context.
An LDLM callback is sent by a server to a client in order to make
it release a lock, on a communication channel that uses a reverse
context. It cannot be refreshed on its own, as it is the 'reverse'
(server-side) representation of a client context.
We do not care if the reverse context is expired, and want to send
the LDLM callback anyway. Once the client receives the AST, it is
its job to refresh its own context if it has expired, hence
refreshing the associated reverse context on server side, before
being able to send the LDLM_CANCEL requested by the server.

Lustre-change: https://review.whamcloud.com/42076
Lustre-commit: 1769f262b96745b61b21fd1450cc4c0386a41b95

Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: Ic8f4fe203f16ed5cfafd3da355c78cf58d96c3eb
Reviewed-on: https://review.whamcloud.com/43173
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Li Xi <lixi@ddn.com>