packages: remove_packages remove more than 1 pkg

As the name of the function suggest, remove_packages shall remove more
than a single package if several are provided as arguments.

The existing code was only considering the first package of a list.

If you did : remove_packages $dir pkg1 pkg2 pkg3 , only pkg1 was
removed.

This situation led to some wrong OS builds as found by Hugo Rosnet.

This patch does now fix it by handling all the arguments as package name.