Update phoenix tests for it to work for both JDBC T2 and T4 drivers

Updated 3 files to allow phoenix tests to work for both T2 and T4:

BaseTest.java:
updated the T2 class path that has been recently changed.

ArithmeticQueryTest.java & VariableLengthPKTest.java:
updated the tests to deal with different error messages and minor different
behaviors on decimal rounding.

Change-Id: I1409605073e9fcfeed3bcecfd9085352c051be3e