Report better capacity info for a limitless 3par cpg

This change has the following improvement:

1. Uses getCPGAvailableSpace from hp3parclient to report
free_capapcity for a limitless cpg.

2. Uses cpg's SDUsage.usedMiB + UsrUsage.usedMiB + free_capacity
to calculate the total_capacity for a limitless cpg. This is the
best we can do for a limitless cpg.

Closes-Bug: #1398651
Change-Id: I62f446786360c61288a788be29d1daa6e409c7b1
Merge "Report better capacity info for a limitless 3par cpg"