Revert "LU-4398 mdt: acquire an open lock for write or execute"

This seems to be causing LU-5197

This reverts commit 97bfe7a3c0fc74fb0e56cbc1ea9cb827fb657b48.
New tag 2.5.2-RC2

Change-Id: I25517c86d132cc7201ed144652fbbb682e2d5b55