IMPALA-6902: Tighten udf test to look for crashes
IMPALA-6902: Tighten udf test to look for crashes

test_native_functions_race assumes that any exception
is grounds for failing the test. However, the flake described
in IMPALA-6902 shows an example of an exception that causes
a false negative (it should be ignored). This change tightens
the test to fail when an impalad crashes, which was the original
intent of the test.

Tests:
- re-ran test_udfs.py

Change-Id: I7780ff328fde5cf462cf718a1467b8a032d2c17b
Reviewed-on: http://gerrit.cloudera.org:8080/10180
Reviewed-by: Thomas Tauber-Marshall <55b5d0aded728f7a3075d2dcc6abf84f96c36406@cloudera.com>
Tested-by: Impala Public Jenkins <039b6b20426ff68ebe492b3021890d8c8fd010c9@cloudera.com>

cloudera/Impala,cloudera/Impala,cloudera/Impala,cloudera/Impala,cloudera/Impala,cloudera/Impala,cloudera/Impala