manager: reformat boolean expression in unit_is_pristine()

Not not IN_SET(…) is just too much for my poor brain. Let's invert
the expression to make it easier to undertand.

(cherry picked from commit b146a7345b69de16e88347acadb3783ffeeaad9d)

Related: #2156620

src/core/unit.c

@@ -4848,12 +4848,12 @@ bool unit_is_pristine(Unit *u) {
          * are marked UNIT_LOADED even though nothing was actually
          * loaded, as those unit types don't require a file on disk. */
 
-        return !(!IN_SET(u->load_state, UNIT_NOT_FOUND, UNIT_LOADED) ||
-                 u->fragment_path ||
-                 u->source_path ||
-                 !strv_isempty(u->dropin_paths) ||
-                 u->job ||
-                 u->merged_into);
+        return IN_SET(u->load_state, UNIT_NOT_FOUND, UNIT_LOADED) &&
+               !u->fragment_path &&
+               !u->source_path &&
+               strv_isempty(u->dropin_paths) &&
+               !u->job &&
+               !u->merged_into;
 }
 
 pid_t unit_control_pid(Unit *u) {