libceph: fix unaligned accesses in ceph_entity_addr handling

GCC9 is throwing a lot of warnings about unaligned access. This patch
fixes some of them by changing most of the sockaddr handling functions
to take a pointer to struct ceph_entity_addr instead of struct
sockaddr_storage.  The lower functions can then make copies or do
unaligned accesses as needed.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>