Fixing client smack tests.

[Issue#]        SSDWSSP-543
[Bug/Feature]   Root privileges are dropped in main test process and remaining
                tests in SECURITY_SERVER_TESTS_CLIENT_SMACK group run with them
                and fail when line with RUNNER_IGNORED_MSG deleted.
[Cause]         Changing test macros from RUNNER_CHILD* to RUNNER_MULTIPROCESS*
                on one smack and one nosmack test resulted in passing dropped
                root privileges in main process to tests run after those. Those
                privileges were held by RUNNER_CHILD* macros.
[Solution]      Keeping that macros for collecting result puposes and running
                both processes droping root privilege in child.
[Verification]  Building and running security-tests.sh ss-clientsmack. No tests
                should fail.

Change-Id: I7b1b4974dedd9a9d1d96e952411aa01cd4f3399b