tst_test.sh: Add sanity checks

Given that when the test is executed the path to the LTP test is in PATH
and that the filename of the script is in $0 we can as well grep the
test source to look for common mistakes on runtime. This just adds a
check if the test calls tst_run function, but the possibilities are much
greater.

Signed-off-by: Cyril Hrubis <chrubis@suse.cz>

testcases/lib/tst_test.sh

@@ -400,3 +400,9 @@ tst_run()
 
 	tst_do_exit
 }
+
+if TST_TEST_PATH=$(which $0) 2>/dev/null; then
+	if ! grep -q tst_run "$TST_TEST_PATH"; then
+		tst_brk TBROK "Test $0 must call tst_run!"
+	fi
+fi