Fix docstrings in keystoneclient

Trusts and service catalog had a few malformed docstrings
that caused warnings when building docs.

Change-Id: Iea8612c3aaebea54c00b02c73c77f0c9e79f86bc
Partial-Bug: #1315523
Merge "Fix docstrings in keystoneclient"
fixed typos found by RETF rules

rules are avaialble at https://en.wikipedia.org/wiki/Wikipedia:AutoWikiBrowser/Typos

Change-Id: I67fb3e0d02c931cb7e605ac74ea8272956afa8e1
Merge "fixed typos found by RETF rules"
Test commit