Add some basic storage kickstart tests

[dwlehman]

I only tested these by installing with the ks files, verifying the results and, in some cases, running the %post manually with set -x to make sure things were behaving as intended.

[mulkieran]

To be correct, the Python code for percent test (third commit) should not use floating point computation and maybe test should show a little more flexibility on numeric value of percent. I'm happy to defer worrying about that until the first time the test detects a spurious error, though, which it may never do.

And, in the first commit, I'm puzzled why it's certain that blkid will have a LABEL key (if install ran correctly).

Other than that, it looks fine to me.

[dwlehman]

I thought floating point math would be adequate for the task given that we're only computing percentages. If this is not necessarily the case I should do it differently.

blkid will always have a LABEL= key for the root LV because I've specified --label=root in the logvol line that defines it.

[dwlehman]

New version with fixed virt-cat invocations. I verified that virt-cat can get stuff from LVs if specified as /dev/<vg>/<lv> or /dev/mapper/<vg>-<lv>.

[dwlehman]

pushed