Improve selinux utils wrappers

Added checks to wrapper scripts for selinux utils. Before running
commands, verify enviromental variables are set and that required files
exists. Return an error code in the event of failure.

Test: Verify audit2allow, audit2why, sediff, seinfo commands still run.
Test: Verify failure if prerequisites are not satisfied.

Change-Id: I3705a90e0a81704829aa5a5feedbfe22aec5fa55
Signed-off-by: Brian Murray <Brian@Clover.com>
4 files changed