Add a regression test for issues #2093 and #2099
Add a regression test for issues #2093 and #2099

Currently querying the Gaia archive can return results from
`gaiadr2.gaia_source` even if the user has specified that they wish to
query a different table. This commit adds a regression test to see if
the right table actually gets queried.

ceb8/astroquery,imbasimba/astroquery,imbasimba/astroquery,ceb8/astroquery