checkpolicy/checkpolicy: Grep for error messages rather than debug logs
    
    checkpolicy was updated in 2.9 in order not to write debug messages on ouput. It
    doesn't output "loading policy ..." messages anymore.
    
    See https://github.com/SELinuxProject/selinux/commit/854fdc1ac40720782491e8ada6837aa4550a7ca1
    
    Fixes:
    [   PASS   ] :: Command 'checkpolicy >& /tmp/tmp.NMYnXbEmez' (Expected 1, got 1)
    [   FAIL   ] :: File '/tmp/tmp.NMYnXbEmez' should contain 'loading policy configuration from policy.conf'
    [   PASS   ] :: Command 'checkpolicy -b >& /tmp/tmp.NMYnXbEmez' (Expected 1, got 1)
    [   FAIL   ] :: File '/tmp/tmp.NMYnXbEmez' should contain 'loading policy configuration from policy'