Sync oslo lockutils to nova

The commit to be merged:

942e1aa Use file locks by default again
ac995be Fix E126 pep8 errors
15b8352 Remove oslo.log from lockutils

942e1aa is hopefully the fix for the "n-cpu stop about 15 minutes 
before the rest of the test run" problem at the gate. We need to 
make sure this actually fixes the gate problem

Closes-Bug: #1349452

Change-Id: I31265d4e08245879ad72d3e91dcd8be2359ca811
Merge "Sync oslo lockutils to nova"