Fix tests failing for SQLite file databases; repair provisioning

Fix tests failing for SQLite file databases; repair provisioning

1. ensure provision.py loads dialect implementations when running
reap_dbs.py.   Reapers haven't been working since
598f2f7e557073f29563d4d567f43931fc03013f .

2. add some exclusion rules to allow the sqlite_file target to work;
add to tox.

3. add reap dbs target for SQLite, repair SQLite drop_db routine
which also wasn't doing the right thing for memory databases
etc.

4. Fix logging in provision files, as the main provision logger
is the one that's enabled by reap_dbs and maybe others, have all
the provision files use the provision logger.

Fixes: #5180
Fixes: #5168
Change-Id: Ibc1b0106394d20f5bcf847f37b09d185f26ac9b5