Fixes re-creating volume on (re)start

When a container is restarted all the volume configs are parsed again.
Even if the volume was already handled in a previous start it was still
calling "FindOrCreateVolume" on the volume repo causing a new volume to
be created.

This wasn't being detected because as part of the mount initialization
it checks to see if the the _mount_ was already initialized, but this
happens after the parsing of the configs.
So a check is added during parsing to skip a volume which was already
created for that container.

Signed-off-by: Brian Goff <cpuguy83@gmail.com>