Improve curl error reporting.

Check for false instead of empty curl response, to make it fall
through to the proper error message in case of an HTTP error.
Add information on which verb is used when an error occurs.
when chroot location exists, offer to remove it
No longer grant access to from the world to the MySQL account.

This is the safe default and sufficient now since only the domserver needs
to access the database. Those running MySQL on a different machine need to
change this default.
Round time difference down to second precision.