backslashes for the double quotes are necessary in the debug lines

backslashes for the double quotes are necessary in the debug lines
otherwise when you run a test run it will print: debug su $user -c "$execstr"
instead of expanding those variables
the backslashes in the output= lines were wrong, but the debug lines
were necessary :)

git-svn-id: http://code.autistici.org/svn/backupninja/trunk@382 758a04ac-41e6-0310-8a23-8373a73cc35d