build: Fix path to /git/calamari-clients

This was hardcoded for the old repo name.  It's still
undesirable for the path here to be hardcoded at all,
but at least this will work with a default-named
checkout.

Signed-off-by: John Spray <john.spray@redhat.com>
(cherry picked from commit 5f7c653541bdee56485afba9ead5faca210a1980)
Fix a few more instances of clients -> calamari-clients
Add definition for rhel7

Signed-off-by: Dan Mick <dan.mick@inktank.com>