ocfs2: don't use handle for locking in allocation functions

ocfs2: don't use handle for locking in allocation functions

Instead we record our state on the allocation context structure which all
callers already know about and lifetime correctly. This means the
reservation functions don't need a handle passed in any more, and we can
also take it off the alloc context.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>