servicemanager: Overwrite old service when a new one is registered

We want to overwrite an old service with the same name as a new service
that is being added. The old one will be cleaned up as servicemanager
loses the reference to it.

Test: atest servicemanager_test && additional tests outlined in Bug
Bug: 162553096
Change-Id: I8835d9f7505367d83a0f29f1d928a07b3d57e56a
diff --git a/cmds/servicemanager/test_sm.cpp b/cmds/servicemanager/test_sm.cpp
index 25245be..fb9f9df 100644
--- a/cmds/servicemanager/test_sm.cpp
+++ b/cmds/servicemanager/test_sm.cpp
@@ -135,6 +135,26 @@
         IServiceManager::DUMP_FLAG_PRIORITY_DEFAULT).isOk());
 }
 
+TEST(AddService, OverwriteExistingService) {
+    auto sm = getPermissiveServiceManager();
+    sp<IBinder> serviceA = getBinder();
+    EXPECT_TRUE(sm->addService("foo", serviceA, false /*allowIsolated*/,
+        IServiceManager::DUMP_FLAG_PRIORITY_DEFAULT).isOk());
+
+    sp<IBinder> outA;
+    EXPECT_TRUE(sm->getService("foo", &outA).isOk());
+    EXPECT_EQ(serviceA, outA);
+
+    // serviceA should be overwritten by serviceB
+    sp<IBinder> serviceB = getBinder();
+    EXPECT_TRUE(sm->addService("foo", serviceB, false /*allowIsolated*/,
+        IServiceManager::DUMP_FLAG_PRIORITY_DEFAULT).isOk());
+
+    sp<IBinder> outB;
+    EXPECT_TRUE(sm->getService("foo", &outB).isOk());
+    EXPECT_EQ(serviceB, outB);
+}
+
 TEST(AddService, NoPermissions) {
     std::unique_ptr<MockAccess> access = std::make_unique<NiceMock<MockAccess>>();