general: avoid direct “rpm -i” invocation

yum maintains its own cache and the direct call of “rpm -i“ is enough
to get it outdated.
common: add TODO regarding cleanup() and pxe.install
Revert "makefile: use simplified targets"

This reverts commit 8e8fd55118a2c2f463c5f0fbe5d6f8f6e69fc464.

A phony target should not be a prerequisite of a real target file.
base: lsb-release is a debian package

redhat-lsb-core is the RHEL package that provides lsb_release