homed: don't drop caches on activation

We should drop caches if we are configured to do so in all cases where
we are done with home dir operations: except if that operation is
activation, because in that case we are not destroying anything, but
leaving it on.

Hence, turn off the flag that reminds us that we should drop caches
before exiting, once activation completed fully,

Follow-up for 86019efa44

src/home/homework-cifs.c

@@ -133,6 +133,7 @@ int home_activate_cifs(
                 return r;
 
         setup->undo_mount = false;
+        setup->do_drop_caches = false;
 
         log_info("Everything completed.");
 

src/home/homework-directory.c

@@ -72,6 +72,8 @@ int home_activate_directory(
                 return r;
         }
 
+        setup->do_drop_caches = false;
+
         log_info("Everything completed.");
 
         *ret_home = TAKE_PTR(new_home);

src/home/homework-luks.c

@@ -1475,6 +1475,7 @@ int home_activate_luks(
         setup->undo_dm = false;
         setup->do_offline_fallocate = false;
         setup->do_mark_clean = false;
+        setup->do_drop_caches = false;
 
         log_info("Everything completed.");