(maint) RPM install should have --oldpackage

Prior to this commit, the RPM package provider would force the
`--oldpackage` option; however, older versions of RPM (i.e. 3.0.5 on
AIX) don't really like `--oldpackage` when you're doing an installation.
Rather than treat it as a NOOP, the older versions of RPM fail. This
commit changes the behaviour so that `--oldpackage` is only used when
the package is an up-/down-grade.

Sprintly: fix item:208
(AIX) Tests for proper usage of --oldpackage w/ RPM

Prior to this commit, there were no tests for installing packages
with the RPM package provider. This commit adds tests to validate
that when a package doesn't already exist `rpm` is called with
`-i`, and when any version is already installed `rpm` is called
with `-U --oldpackage`. These tests are important because older
versions of RPM, such as 3.0.5 on AIX, barf when `--oldpackage` is
applied with `-i` whereas newer versions of RPM simply treat it as
a NOOP because it doesn't make sense with `-i`.

Sprintly: fix ticket:208