make.bash: stricter selinux test
make.bash: stricter selinux test

SELinux can be installed but not turned on.
Don't complain unless it is actually turned on.

https://bugzilla.redhat.com/show_bug.cgi?id=652987#c20

R=agl
CC=golang-dev
http://codereview.appspot.com/3979044
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go