Provides macro for easy backup of libprivilege DB

Provides macro for easy backup of libprivilege DB

[Issue#]        SSDWSSP-732
[Feature]       Implement better DB management in our libprivilege-control tests.
[Cause]         It was not possible to withdraw changes done by some of the tests.
                As a result some of the DB changes were permanent.
[Solution]      Provide a macro which backups DB before each test and copies it back
                after the test.
[Verification]  Build and run on the target.

Change-Id: I2c46c69ee3cc122bc8567e5f97ed9530940bb508