IMPALA-839: Update tests to be more thorough when run exhaustively

Some tests have constraints that were there only to help reduce runtime which
reduces coverage when running in exhaustive mode. The majority of the constraints
are because it adds no value to run the test across additional dimensions (or
it is invalid to run with those dimensions). Updates the tests that have
legitimate constraints to use two new helper methods for constraining the table format
dimension:
create_uncompressed_text_dimension()
create_parquet_dimension()

These will create a dimension that will produce a single test vector, either
uncompressed text or parquet respectively.

Change-Id: Id85387c1efd5d192f8059ef89934933389bfe247
Reviewed-on: http://gerrit.ent.cloudera.com:8080/2149
Reviewed-by: Lenni Kuff <lskuff@cloudera.com>
Tested-by: jenkins
IMPALA-914: Map null type to boolean in JDBC to be compatible with Hive.

Change-Id: I5831ae7d5dcb03aecea4138d0b13487898951068
Reviewed-on: http://gerrit.ent.cloudera.com:8080/2279
Reviewed-by: Nong Li <nong@cloudera.com>
Tested-by: jenkins