Fixed LIKE predicate %% pattern error

Before:
Query: select count(*) from functional.alltypes where date_string_col
like "%%"
+----------+
| count(*) |
+----------+
| 0        |
+----------+
After:
Query: select count(*) from functional.alltypes where date_string_col
like "%%"
+----------+
| count(*) |
+----------+
| 7300     |
+----------+

Change-Id: Ic2f047ba3b03eeebe9477892da95a1d06dc27da7
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/3768
Reviewed-by: Paden Tomasello <paden.tomasello@cloudera.com>
Tested-by: jenkins