Modify v21 alias name for compatible with v2

This patch changes some of the alias names to be compatible with v2.
so the extension info output will be as same with v2.
 consoles -> os-consoles
 flavor-extra-specs -> os-flavor-extra-specs
 flavor-manage -> os-flavor-manage

Partially implements blueprint v2-on-v3-api

Change-Id: Ia8c6a0144e43134667636db9ba862b26f265a433
Merge "Modify v21 alias name for compatible with v2"