Fix running tests when building out of the source tree.

CMake's enable_testing needs to be called from the root of the project
as well for CTest to discover the tests in the build tree.  This is
covered in CMake's manual in section 7.2.17 enable_testing.

Change-Id: I7c9b845c52064ff83e39b483b76137b529c1a9a4

CMakeLists.txt

@@ -1030,5 +1030,6 @@ qt_finalize_executable(${PROJECT_NAME})
 # tests
 if(BUILD_TESTING)
   message("Add Jami tests")
+  enable_testing()
   add_subdirectory(${TESTS_DIR})
 endif()