Drop tables in Dispose() for ConversionTests

[johnnypham]

Attempt to fix #1230

The queries to drop the tables are moved from the end of each test method to Dispose(), to drop the tables before dropping the CEKs.

[DavoudEshtehari]

It seems reasonable, and I couldn't see any issue with it. Just be cautious! We had a known intermittent issue with AE tests, which were related to the Dispose functionality in the fixture on facing any exception.

cc @JRahnama

[JRahnama]

It seems reasonable, and I couldn't see any issue with it. Just be cautious! We had a known intermittent issue with AE tests, which were related to the Dispose functionality in the fixture on facing any exception.

The issue is a known issue, as far as I could research, in XUnit when using IClassFixture. The dispose is not called till all the tests related to the fixture is ran to completion. If the tests are stopped or aborted at the middle no Dispose is called to clean up after.

However, As Davoud mentioned we wont know the result till we see the tests in action with this change as the issue was happening intermittently. Looks good to as well.