The issue is that we want to install os-brick from source, but if we
do this using upper-constraints on the install, it will fail. This
patch modifies the tox install command used by appropriate testenvs
so it will create and use a local constraints file with os-brick
removed.
The local u-c file is named 'local-upper-constraints.txt'. The
constraints file used can be overridden via the
CINDERLIB_CONSTRAINTS_FILE environment variable.
Change-Id: I8cb4085dd465043a783c974886f56e49820871a1
e4dd75a3b4