Reorganize/reduce end to end test time.

This patch does a few things:
1) Move the metadata tests into their own folder under tests/. I think it's useful to
loosely categorize them so it's easier to run a subset of the tests that are most
useful for the changes you are making.

2) Reduce the test vectors for query_tests. We should have identical coverage in
the daily exhaustive runs but the normal runs should be much better. In particular,
deemphasizing scanner tests since that code is more stable now.

3) Misc test cleanup/consolidate python test files/etc.

Change-Id: I03c2f34877aed192c2a50665bd5e15fa85e12f1e
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/3831
Tested-by: jenkins
Reviewed-by: Nong Li <nong@cloudera.com>