ima_measurements.sh: Check policy for test3

This allows the test to work even without specifying ima_policy=tcb on
the boot command line.

Link: https://lore.kernel.org/ltp/20250114112915.610297-10-pvorel@suse.cz/
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Petr Vorel <pvorel@suse.cz>

Author: pevik

testcases/kernel/security/integrity/ima/tests/ima_measurements.sh

@@ -77,6 +77,11 @@ test3()
 	tst_res TINFO "verify not measuring user files"
 	tst_check_cmds sudo || return
 
+	if [ "$IMA_POLICY_CHECKED" != 1 ]; then
+		tst_res TCONF "test requires specific policy, try load it with LTP_IMA_LOAD_POLICY=1"
+		return
+	fi
+
 	if ! id $user >/dev/null 2>/dev/null; then
 		tst_res TCONF "missing system user $user (wrong installation)"
 		return