Make compute-trust.json compatible with TrustFilter

Current properties inside compute-trust.json does not match
with how TrustFilter in nova works. JSON provides True/False
boolean values but TrustFilter expects trusted/untrusted/unknown
string values. This patch repairs compute-trust.json to be
compatible with TrustFilter.

Change-Id: I26965a549daf9340621b0f18a1b845b39bac4bd8
Closes-Bug: #1369581
Merge "Make compute-trust.json compatible with TrustFilter"