Fix double-callback-call crash in //chromeos/services/network_config/

Fix bug found by the "bugprone-use-after-move" clang-tidy check.

Bug: 1122844
Change-Id: I3420b6c260b9fa94847b9b63df0438a9bce0b1c7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2556838
Commit-Queue: Steven Bennetts <stevenjb@chromium.org>
Auto-Submit: Maksim Ivanov <emaxx@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#831916}

chromeos/services/network_config/cros_network_config.cc

@@ -2000,6 +2000,7 @@ void CrosNetworkConfig::SetProperties(const std::string& guid,
           << "SetProperties called with ethernet.eap but no EAP config: "
           << guid;
       std::move(callback).Run(false, kErrorNetworkUnavailable);
+      return;
     }
     network = eap_state;
   }