Add missing break statement to make sure all 3DES etypes really are treated

the same.

CID:		3624
Found with:	Coverity Prevent(tm)
Reviewed by:	dfr
MFC after:	1 week

sys/kgssapi/krb5/krb5_mech.c

@@ -288,6 +288,7 @@ get_keys(struct krb5_context *kc)
 	case ETYPE_DES3_CBC_SHA1:
 	case ETYPE_OLD_DES3_CBC_SHA1:
 		etype = ETYPE_DES3_CBC_SHA1;
+		break;
 
 	default:
 		etype = keydata->kk_type;