BF-532: Revert "SERVER-14668: Replace uses of DBWrite lock with DBLock"

This reverts commit ae333bc94a7d89d3220dcae9579fcaf68aa2e290.
This reverts commit 962f959a09b63aa0482d7e0c9bad89363d1e1194.
SERVER-13635: honor --storageEngine option in spawned processes
Merge remote-tracking branch 'upstream/master'