[PATCH] Debian packaging: extend libcrack hack to create correct control file

When the debian/control gets stripped off the libcrack3 dependency,
it should also strip off the mariadb-cracklib-password-check-10.2
package entry, otherwise the resulting Debian source package will
not be re-buildable independently later.

Successful build visible at https://launchpad.net/~mysql-ubuntu/+archive/ubuntu/mariadb-10.2/+builds?build_text=&build_state=all (ppc64 build for e717ceb, the other builds fail due to inherited other problems in current 10.2 master). Builds at https://buildbot.askmonty.org/buildbot/grid?branch=ok-debpkg-10.2&category=main also fail due to inherited problems from current 10.2 master, so it is not useful for QA in at the moment.