* make all change in selinux mode persistent

* rework code to correspond with comments obtain from review about duplicity and useless code

* repair bad indent, remove bracket

Change-Id: I45c932cf18dbc1073a86cbab272d2dda9f15fa41

"names" makes a separate call to the package management frontend to
install each package, whereas "pkgs" makes just a single call so that it
improves performance.