Med: Improve script.sh's error reporting

The script agent used primarily by rgmanager had a very minimal amount
of error reporting, such that it could be very confusing as to why a
script resource had failed.

This patch looks for a variety of errors from the script resource.

Updated patch fixes concerns from Jan Pokorný

Resolves: rhbz#773478

Signed-off-by: Lon Hohberger <lhh@redhat.com>