Fix Membership list loading bug

When loading a page on its own that contains the membership workflow,
the member lists would not get populated.

Also include a Selenium unit test to avoid similar regressions in the
future.

Change-Id: I5f23da271313f3ddf4acded221864ef5ba83f0eb
Closes-Bug: #1288270
Fix unbound local error in instance DetailView

If an error is raised in the instance DetailView we assume that a
redirect will be raised. However, certain exception classes will not
result in a redirect when handled by the standard Horizon exception
handler. If the error handler doesn't re-raise some sort of error,
control will be returned to the statement after the except block and
some of the necessary local variables may be unbound.

This fix simply ensures that an errors result in a redirect so that
we never end-up in a situation where the instance variable is unbound.

Change-Id: Ica9a09c9236bb50206277425633d63a8e7387401
Closes-Bug: 1291021
Error message in create vol with a vol source

Updating the error message in the create volume form
for the case where the volume source is another volume
and the current volume size is less than the volume source

Change-Id: I53d5e9ffdea4344bafcaf3e0623e2e39c4c259be
Closes-Bug: #1291244
Merge "Error message in create vol with a vol source"
Merge "Fix Membership list loading bug"
Merge "Fix unbound local error in instance DetailView"