Unit test failed when run function related test with Interpreter Tests.

[ywqzzy]

Bug Report

Thanks to @SchrodingerZhu. He ran across this bug and helped me figure out how it happened.

1. Minimal reproduce step (Required)

./dbms/gtests_dbms --gtest_filter="*Date*:*Join*"

2. What did you expect to see? (Required)

All test passed.

3. What did you see instead (Required)

4. What is your TiFlash version? (Required)

Nightly

[ywqzzy]

When multiple Function tests run, the unit test will call DB::registerFunctions() multiple times, then in the InterpreterTest::SetUpTestCase(), it will raise an exception, lead to the DB::registerAggregationFunction() not called.
It's better to wrap it into anthor "try...catch block".
Current code:

Modified code: