TAJO-913: Add some missed tests for constant value group-by keys.

Closes #60
TAJO-925: Child ExecutionBlock of JOIN node has different number of shuffle keys. (Hyoungjun Kim via hyunsik)

Closes #61
TAJO-927: Broadcast Join with Large, Small, Large, Small tables makes a wrong plan. (Hyoungjun Kim via hyunsik)

Closes #65
TAJO-929: Broadcast join with empty outer join table returns empty result. (Hyoungjun Kim via hyunsik)

Closes #66
TAJO-934: Multiple DISTINCT returns null grouping key value. (Hyoungjun Kim via hyunsik)

Closes #63
TAJO-852: Integration test using HCatalog as a catalog store is failed. (jinho)
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into TAJO-932
TAJO-926: Join condition including column references of a row-preserving table in left outer join causes incorrect result.

Closes #62
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/tajo into TAJO-932