minstall: restore_selinux_contexts: fix env test
minstall: restore_selinux_contexts: fix env test

To avoid extra env test, test destdir presence
upper in restore_selinux_contexts

mesonbuild/meson,pexip/meson,mesonbuild/meson,mesonbuild/meson,jpakkane/meson,jpakkane/meson,pexip/meson,jpakkane/meson,jpakkane/meson,mesonbuild/meson,pexip/meson,pexip/meson,pexip/meson,mesonbuild/meson,pexip/meson,pexip/meson,jpakkane/meson,jpakkane/meson,pexip/meson,mesonbuild/meson,mesonbuild/meson,jpakkane/meson,jpakkane/meson,mesonbuild/meson,pexip/meson,jpakkane/meson,pexip/meson,mesonbuild/meson,mesonbuild/meson