Print last 200 lines of update_engine.log from failed update.
Print last 200 lines of update_engine.log from failed update.

Change-Id: I0dbc760007038086b94d534d497a7f72b957f365

BUG=
TEST=Ran it on a failed update.

Review URL: http://codereview.chromium.org/4137003

coreos/scripts,andrejro/coreos--scripts,smilart/scripts,vmware/coreos-scripts,smilart/scripts,endocode/scripts,nicescale/scripts,bcwaldon/coreos-scripts,bcwaldon/coreos-scripts,fivethreeo/scripts,zhang0137/scripts,sigma/coreos-scripts,fivethreeo/scripts,zhang0137/scripts,andrejro/coreos--scripts,endocode/scripts,BugRoger/scripts,marineam/coreos-scripts,trnubo/scripts,mjg59/scripts,BugRoger/scripts,gtank/scripts,nicescale/scripts,fivethreeo/scripts,zhang0137/scripts,crawford/scripts,trnubo/scripts,bcwaldon/coreos-scripts,mischief/scripts,sigma/coreos-scripts,glevand/coreos--scripts,crawford/scripts,andrejro/coreos--scripts,glevand/coreos--scripts,crawford/scripts,endocode/scripts,nicescale/scripts,mischief/scripts,vmware/coreos-scripts,gtank/scripts,marineam/coreos-scripts,gtank/scripts,trnubo/scripts,vmware/coreos-scripts,mischief/scripts,mjg59/scripts,sigma/coreos-scripts,marineam/coreos-scripts,BugRoger/scripts,smilart/scripts,mjg59/scripts,coreos/scripts