dlm: fix up memory allocation flags

Use ls_allocation for memory allocations, which a cluster fs sets to
GFP_NOFS.  Use GFP_NOFS for allocations when no lockspace struct is
available.  Taking dlm locks needs to avoid calling back into the
cluster fs because write-out can require taking dlm locks.

Cc: Christine Caulfield <ccaulfie@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>