scripts: install-deps.sh: Fix distribution detection
scripts: install-deps.sh: Fix distribution detection

Relying on the installed package manager to detect the distribution
is not reliable since it's possible to install multiple package managers
at the same time. As such, lets simply use the information in the
os-release files.

Change-Id: I285c6cd94932f84bb9133b39d282c39d9a25b301

openstack/bifrost,openstack/bifrost