Fix a typo of tabstop

Only in nova/compute/manager.py, there is 'tabstop=6'. This change was
introduced at commit:2d0578c5. But this is an unintentional change.
This commit fix it to the same as others.

Change-Id: I5c4ffe354e2d37caa231de561ac257f23c6ab7d5
Merge "Fix a typo of tabstop"