Change how we run e2fsck to check ext filesystems
Change how we run e2fsck to check ext filesystems

The '-p' option means "Automatically repair ("preen") the file system.  This
option will cause e2fsck to automatically fix any filesystem problems that can
be safely fixed without human intervention." which is something we really
shouldn't do as part of reset()/populate(). We should use '-n' instead "Open the
filesystem read-only, and assume an answer of `no' to all questions." which
guaranties no changes to be made on the file system.

We might want to add the '-p' functionality back at some point, but it needs to
be explicitly triggered by the user code (e.g. Anaconda). I think we need to add
a 'clean' property and a 'repair' method to the formats.FS class so that users
can see where the problem is (if any) and explicitly trigger a safe fixup
attempt if they want to.

Related: rhbz#1170803

rhinstaller/blivet,vojtechtrefny/blivet,rvykydal/blivet,vojtechtrefny/blivet,rhinstaller/blivet,jkonecny12/blivet,jkonecny12/blivet,rvykydal/blivet