Adds V3 API samples for evacuate,ext-az,ext-serv-attrs

Partially implements blueprint v3-api-unittests
Partially implements blueprint v3-api-specification

Change-Id: I340456ba688bad4a42d66247899ee9f494fb429c
Adds evacuate,ext-avail-zone,ext-ser-attrs metafiles for api samples

Converts evacuate,extended-available-zone,extended-servers-attributes
api sample to create meta files for api sample docs.
We use this to auto generate the specification document

Change-Id: Ie6f0e198b1d090fdec7a3a084889dfef6681d13e