Logical error in flavors unset_keys method

When we want to unset multi keys of flavor
extra data, only first key can be removed
because of the key word named 'return'.
To fix it, remove the return key word

Change-Id: I70d1f2e84a2bfcea1db60b26138f84421f9a7309
Closes-bug: #1324077
Add NOVACLIENT_BYPASS_URL env variable

Currently, in order to use a bypass URL, you need to specify it using the
`--bypass-url` command-line option each time, which is inconvenient if you
plan on always using a bypass URL.

This patch adds a `NOVACLIENT_BYPASS_URL` environment variable which can be
placed in the `novarc` to persistently set this option.

Change-Id: I49e67ee1fc3570a43e49dc1d78d8ca0b26945bc8
Closes-Bug: 1326134
Merge "Add NOVACLIENT_BYPASS_URL env variable"
Merge "Logical error in flavors unset_keys method"