make swift-proxy rely on glance before relation

since glance is one of the core services to always be up and
swift-proxy is optional we make switf-proxy relate to glance
rather than the opposite.

Signed-off-by: Adam Stokes <adam.stokes@ubuntu.com>
Merge pull request #51 from battlemidget/patch-make-swift-proxy-relate-glance

make swift-proxy rely on glance before relation