IMPALA-1508: don't JIT TimestampFunctions::DateAddSub

For some reason, the try/catch added to fix IMPALA-1493 doesn't work
when we JIT the function. Fixing this in the JIT'd code will take some
time, so for now just don't JIT the function.

Change-Id: I7b2801027db0a9deb19b477c1a4ca0bdad77a825
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/5383
Reviewed-by: Skye Wanderman-Milne <skye@cloudera.com>
Tested-by: jenkins