Fix internal scheme tests

Fix internal scheme tests

1. Regular std::exception is not reported as error by boost test.
   Std::runtime_error is used because a part of the test code is also used in
   a tool for database generation.

   This commit replaces calls to boost test macros with calls to a wrapper macro
   which is expanded to std::runtime_error or boost test assert depending on a
   compilation flag.

2. Test binaries are modifying process labels which requires onlycap.

   This commit modifies exec label and adds onlycap fixture to disable onlycap
   for scheme tests.

Change-Id: Ibbe44c2bca6e12b5ade360b267c281ef18294258