TestCMakeFileApi: fix slot name: initTestSuite => initTestCase

d38ae65b apparently misnamed this slot,
which initializes AutoTestShell and TestCore, by mistake. The test
succeeded only because the two test functions - initTestSuite() and
testConfigure() - were always called in the same order.

Running a single test function via
`./bin/test_cmakefileapi testConfigure` caused a Segmentation fault at
the first line of testConfigure().