Cleanups for ligolw_segment_insert_dqsegdb
requested to merge github/fork/duncanmmacleod/clean-ligolw_segment_insert_dqsegdb into dqsegdb_2.0.0
This PR cleans up the import
blocks in ligolw_segment_insert_dqsegdb
to make things more readable, and to remove the import protections that are unnecessary. This also removes the creation of the ldbd.LIGOMetadata
object, which is then never used.