jdbc unit tests -- connection caching

[Hanifi Gunes <hg...@maprtech.com>]

Folks,

I have been working on DRILL-2127 to enable connection caching in the jdbc
test suites. The patch provides a convenience method for creating a
connection via JdbcTest#connect. The caching happens transparently. Dev's
should not be concerned about explicitly caching a connection. As a good
practice, however, we should still write clean, integrant unit tests,
freeing the resources after use. This should include closing any
connections created in the test case imho.

I just wanted to inform everyone about the patch so that new jdbc unit
tests could hopefully leverage the caching which seems to reduce test
runtime substantially. On my setup jdbc tests went from ~6:30 down to ~4:30
mins.

Let me know.

Regards.
-Hanifi