Make the mac_portacl testcases work / more robust

Make the mac_portacl testcases work / more robust

- A trap(1) call has been added to the test scripts to better
  ensure that the tests do a better job at trying to restore the
  test host state at the end of the tests (if the test was
  interrupted before it would leave the system in an odd state,
  potentially making the test results for subsequent runs
  non-deterministic).
- Add root user checks
- Fix nc(1) usage:
  -- -o is deprecated
  -- Using `-w 10` will make the call timeout after 10 seconds so it
     doesn't block indefinitely
- Use local variables
- Be more terse in the error messages
- Parameterize out "127.0.0.1"

MFC after: 1 week
Sponsored by: EMC / Isilon Storage Division