Don't hardcode glance protocol when finding trove guest image

This allows configuration of trove when devstack is configured
for SSL or tls-proxy.

Change-Id: I680effda94926951f9068e2df1e354c708aa4495
Add options to enable using DHCP agent Metadata-proxy

Add options to support DHCP agent providing metadata-proxy.
In some cases, users have to disable L3 Agent. But people still
need metadata services.

Change-Id: I4664fc3a4937c3b7b5c27e74f509b683ffbedd09
Merge "Don't hardcode glance protocol when finding trove guest image"
Merge "Add options to enable using DHCP agent Metadata-proxy"