Catch all exceptions from corpus pruning tasks. (#1617)
Catch all exceptions from corpus pruning tasks. (#1617)

* Catch all exceptions from corpus pruning tasks.

This catches exceptions that come over grpc channel from OSS-Fuzz
worker bots for the same CorpusPruningException.

* Fix lint.
google/clusterfuzz,google/clusterfuzz,google/clusterfuzz,google/clusterfuzz,google/clusterfuzz,google/clusterfuzz,google/clusterfuzz,google/clusterfuzz