audit: fix dangling keywords in integrity ima message output

Replace spaces in op keyword labels in log output since userspace audit tools
can't parse orphaned keywords.

Reported-by: Steve Grubb <sgrubb@redhat.com>
Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c
index d3113d4..59ac902 100644
--- a/security/integrity/ima/ima_appraise.c
+++ b/security/integrity/ima/ima_appraise.c
@@ -214,7 +214,7 @@
 		hash_start = 1;
 	case IMA_XATTR_DIGEST:
 		if (iint->flags & IMA_DIGSIG_REQUIRED) {
-			cause = "IMA signature required";
+			cause = "IMA-signature-required";
 			status = INTEGRITY_FAIL;
 			break;
 		}