TestPlatform: return different error code for different failure
TestPlatform: return different error code for different failure

In order to detect the error type when only the error code is
accessible (legacy tests):
 - return 1, 2 or 3 if the arguments could not be parse successfully
 - return -1 if it is a server error

Signed-off-by: Kevin Rocard <f6672397850e914591889d29dcaf9077eb1a8a4f@intel.com>

01org/parameter-framework,clero/parameter-framework,dawagner/parameter-framework,01org/parameter-framework,mgaio/parameter-framework,miguelgaio/parameter-framework,mgaio/parameter-framework,miguelgaio/parameter-framework,krocard/parameter-framework,miguelgaio/parameter-framework,clero/parameter-framework,mgaio/parameter-framework,01org/parameter-framework,dawagner/parameter-framework,krocard/parameter-framework,dawagner/parameter-framework,clero/parameter-framework,krocard/parameter-framework