toollib: close connection to lvmetad after fork

toollib: close connection to lvmetad after fork

sharing connection between parent command and background
processes spawned from parent could lead to occasional failures
due to unexpected corruption in daemon responses sent to either child
or a parent.

lvmetad issued warning about duplicate config values in request.
LVM commands occasionaly failed w/ internal error after receving
corrupted response.

lvmetad connection is renewed when needed after explicit disconnect
in child