Fix cmakeloadprojecttest.

Looks like it was broken by 6c6b4fe7f4b62a8c03dcd1cefaa5fda2035f6def.

There are two issues related to that commit:
* "test" target is renamed into "testkde4app" in the
kde4app/CMakeLists.txt and not renamed in the test code.
* Disapeared target "buildtests" is generated only when

KDE4_BUILD_TESTS is False according to the kde4_add_unit_test macro
implementation. Now it set tot True exolicitely to elliminate
dependency on developer environment.

REVIEW: 107453