Support non-default ctdbd socket paths

Read the ctdbd socket path from smb.conf, rather than assuming the
default; (bnc#893154).
- 3.1.12

Signed-off-by: David Disseldorp <ddiss@suse.de>
Merge pull request #31 from ddiss/ctdb_socket_arg_v2

Support non-default ctdbd socket paths