Tidy error handling in bloom code.
Tidy error path in LSM truncation.

Based on Coverity resource leak ID 1129049:
Resource leak (RESOURCE_LEAK)
leaked_storage: Variable "chunk" going out of scope leaks the
storage it points to.
Shuffle shared cache cleanup code to be clearer..

Will hopefully resolve Coverity report 1129036:
Missing unlock (LOCK)
24. missing_unlock: Returning without unlocking
"__wt_process.cache_pool->cache_pool_lock.lock".

Though I don't see how the unlock could be missed.