Look for all accessible flavors by default, not just public ones

The Nova server will restrict unprivileged user accounts to just
public images, while allowing administrator accounts access to
all. The Nova client shouldn't force the flavor name lookup to
be restricted to just public images, since that breaks the ability
to the flavor name when booting an instance

Fixes bug #1327212

Change-Id: I949aec52660242249b8cba51d77bfdc1acaf31d2
Merge "Look for all accessible flavors by default, not just public ones"