Actually use the check for prior initialization in sudo_getdomainname().

plugins/sudoers/match.c

@@ -916,6 +916,7 @@ sudo_getdomainname(void)
     static char buf[HOST_NAME_MAX + 1];
     static bool initialized;
 
+    if (!initialized) {
 	if (getdomainname(buf, sizeof(buf)) == 0 && buf[0] != '\0') {
 	    char *cp;
 
@@ -929,6 +930,7 @@ sudo_getdomainname(void)
 	    }
 	}
 	initialized = true;
+    }
 #endif /* HAVE_GETDOMAINNAME */
     return domain;
 }