VMM/handler: Use more common.lisdir() in Handler's methods _chkenv,
_delete_domain_dir, _delete_home, _get_disk_usage, _make_domain_dir,
and _make_home.
Handler._make_home(): Also check if the domain directory exists.
# All parameters are described in pgsql_table(5) / PGSQL PARAMETERS
#
# The hosts that Postfix will try to connect to and query from.
hosts = localhost
# The user name and password to log into the pgsql server.
user = postfix
password = some_password
# The database name on the servers.
dbname = mailsys
# The SQL query template used to search the database
query = SELECT gid FROM postfix_gid WHERE domainname='%s'