docs: Add another way to view the Synnefo UI

Add instructions on how to connect to the Synnefo UI using a SOCKS
proxy.
deploy: Remove obsolete UI_MEDIA_URL setting

Deploy used to set UI_MEDIA_URL to point to the IP of the host
instead of its FQDN, to work around issues with the Java-based VNC
client and self-signed certificates. Synnefo v0.16 has obsoleted
the Java VNC console, so we may safely remove this setting.
Fix burnin bug: Index error in pithos account_get

Bug description: pithos test assumed there are always some extra
containers in the tested pithos account and checked for their
existence, causing an Index error to be raised when starting the
test with an empty account.

Solution: Do not check for containers outside the ones created
specifically for the test.