LU-10467 ptlrpc: convert waiting in sptlrpc_req_refresh_ctx()

LU-10467 ptlrpc: convert waiting in sptlrpc_req_refresh_ctx()

The l_wait_event call in sptlrpc_req_refresh_ctx() is somewhat complex
as it is passed both an on_timeout and on_signal handler, and
on_timeout doesn't return a constant value.

The net effect is to wait for the timeout with signals blocked.  Then,
if the condition still isn't true, run the on_timeout handler and if
that returns zero, wait again - indefinitely this time - and allow
some signals.  If a signal was received, call the on_signal handler.

This is fairly straight forward to write out in C, as shown in the
patch.

Change-Id: I7f9cfb8a8ff234bed4045ab21b53d018337cd615
Signed-off-by: Mr NeilBrown <neilb@suse.com>
Reviewed-on: https://review.whamcloud.com/35987
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>