Fix iterator in ServiceManager::removeCallback

The pointer to the iterator in this function wasn't properly dereferenced, leading to an inifinite loop in ServiceManager::binderDied.

Bug: 144534962
Test: Manual (boot and dynamically start services)
Change-Id: Ie7b8685b5de31ab7c9ba5877b6df3af08aab0c0f
diff --git a/cmds/servicemanager/ServiceManager.cpp b/cmds/servicemanager/ServiceManager.cpp
index 861401c..adecc3c 100644
--- a/cmds/servicemanager/ServiceManager.cpp
+++ b/cmds/servicemanager/ServiceManager.cpp
@@ -306,7 +306,7 @@
     if (listeners.empty()) {
         *it = mNameToCallback.erase(*it);
     } else {
-        it++;
+        (*it)++;
     }
 }