Fix handling of control files for DEB packages. (#21940)

Due to a typo in the CPack configuration, the main `netdata` package control files were being included in any package that did not explicitly define own control files, causing uninstallation of those packages to mask the netdata service. Fix this so that we set the control files for the main package itself instead of specifying them as the default for any package that doesn’t define it’s own control files.