Log the update test result error instead of throwing an exception.

Summary:
For some unknown reasons, our test framework fails to update test
results occasionally. Instead of throwing a nasty exception, log
the error message. This will help us to figure out the real reason
behind the error.

Test Plan:
arc lint.

Reviewed By: epriestley
Reviewers: jungejason, epriestley
CC: epriestley, aran
Differential Revision: 463