The "checkupdates" compound statement (" ... || ... && ...") did not
work due to the equal precendence of both operators (introduced in
6cb5c9e104).
Closes: #1004
Thanks to Ken-ichi Mito for reporting this issue.
No more environment variables since those can easily be configured with
regular munin settings.
Properly quote all strings.
No longer use temp files for holding update information; instead hold it
all in a variable.