MD5: Abort on errors for cmdline nandroid restore

If 'nandroid restore' is run from the command line, prompts are not
possible (thanks to Phyto Wardt for pointing this out). Abort with a
listing of files that are missing from directory or nandroid.md5.

Change-Id: I527ffeafc5da50e7878ddc103f4fb55218632ce1