dlm: rearrange async condition return

[ Upstream commit a800ba77fd285c6391a82819867ac64e9ab3af46 ]

This patch moves the return of FILE_LOCK_DEFERRED a little bit earlier
than checking afterwards again if the request was an asynchronous request.

Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>
Stable-dep-of: 59e45c758ca1 ("fs: dlm: interrupt posix locks only when process is killed")
Signed-off-by: Sasha Levin <sashal@kernel.org>