systemctl: convert return value of install_client_side() to enum

The checks are reordered to do checks that don't require interacting with the
system first.

src/systemctl/systemctl-util.c

@@ -523,7 +523,7 @@ int unit_find_paths(
 
         /* Go via the bus to acquire the path, unless we are explicitly told not to, or when the unit name is a template */
         if (!force_client_side &&
-            !install_client_side() &&
+            install_client_side() == INSTALL_CLIENT_SIDE_NO &&
             !unit_name_is_valid(unit_name, UNIT_NAME_TEMPLATE)) {
                 _cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
                 _cleanup_free_ char *load_state = NULL, *dbus_path = NULL;
@@ -880,26 +880,27 @@ bool output_show_unit(const UnitInfo *u, char **patterns) {
         return true;
 }
 
-bool install_client_side(void) {
-        /* Decides when to execute enable/disable/... operations client-side rather than server-side. */
-
-        if (running_in_chroot_or_offline())
-                return true;
-
-        if (sd_booted() <= 0)
-                return true;
-
-        if (!isempty(arg_root))
-                return true;
-
-        if (arg_runtime_scope == RUNTIME_SCOPE_GLOBAL)
-                return true;
+InstallClientSide install_client_side(void) {
+        /* Decides whether to execute enable/disable/… client-side offline operation rather than
+         * server-side. */
 
         /* Unsupported environment variable, mostly for debugging purposes */
         if (getenv_bool("SYSTEMCTL_INSTALL_CLIENT_SIDE") > 0)
-                return true;
+                return INSTALL_CLIENT_SIDE_OVERRIDE;
 
-        return false;
+        if (!isempty(arg_root))
+                return INSTALL_CLIENT_SIDE_ARG_ROOT;
+
+        if (running_in_chroot_or_offline())
+                return INSTALL_CLIENT_SIDE_OFFLINE;
+
+        if (sd_booted() <= 0)
+                return INSTALL_CLIENT_SIDE_NOT_BOOTED;
+
+        if (arg_runtime_scope == RUNTIME_SCOPE_GLOBAL)
+                return INSTALL_CLIENT_SIDE_GLOBAL_SCOPE;
+
+        return INSTALL_CLIENT_SIDE_NO;
 }
 
 int output_table(Table *table) {