Revert "VMware Driver update correct disk usage stat"

This reverts commit 9adba6727bbec051c1437ee95367ecb97b207f35.

Reporting aggregate storage space is not correct, since the nova
scheduler will assume that it can send a guest of that size to
the node, which the node will be unable to support due to lack of
contiguous disk space. The previous behavior was correct, where
the largest available chunk was reported.

Change-Id: Ia3a6e3f502282d44473d4908f68d71a97167e85f
Merge "Revert "VMware Driver update correct disk usage stat""