auto-repair package list update problems

leap deploy blah
 - [blah] failed to update packages
 - [blah] trying to run apt-get update again
 - [blah] failed to update packages again
 - [blah] trying another package mirror.. (mv /etc/apt/sources.list.d/secondary.list.disabled /etc/apt/sources.list.d/secondary.list mv /etc/apt/sources.list /etc/apt/sources.list.disabled apt-get update) 
 - [blah] update packages succeeded
 - [blah] running apply (second try)

If the apt source that fails is the deb.leap.se source, then we have a hard dependency on something there, and we need to stop and let the admin know with a nice message (#2353 (closed))

Due to the fact that 'apt-get update' exits with an exit-code 0, "even if it fails":https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=696335 do not depend on the result code and instead parse the output for possible errors

(from redmine: created on 2012-12-06, relates #1237 (closed), relates #1016 (closed), relates #1348 (closed), relates #1609, relates #2353 (closed))