Really read files on dry runs

We need to load configuration and examine filesystem on
dry runs to pretend to issue correct commands.

Change-Id: I525ca5c3b1847e837e85305cb67b7635b865e2df
Raise exceptions when some programs fail to start

We should not show happy cow when some programs failed to start,
and we should not record the phase as successful in that case.

Partially fixes: bug #1192675

Change-Id: I022ba6db01640551ffdcb2e7301e559e22fc9a9e
Merge "Really read files on dry runs" into stable/grizzly
Merge "Raise exceptions when some programs fail to start" into stable/grizzly