Add tests for procctl(2): process-control audit class

[aniketp]

Summary

This revision introduces two atf-c(3) test-cases for verifying the auditability of
procctl(2) system call. The audit class is process-control

Test Plan

Execute make && make install from test/sys/audit.
Execute kyua test from /usr/tests/sys/audit. All testcases should succeed.