init: ServiceList FindInterface

FindService can't be used w/ interfaces due
to the fact that multiple interfaces can be
added to any given interface.

Bug: 79418581
Test: boot device, manually use ctl commands
Change-Id: I7c152630462c9b7509473bc190f5b30460fcc2bc
diff --git a/init/service.h b/init/service.h
index cf38f69..9cb35b8 100644
--- a/init/service.h
+++ b/init/service.h
@@ -244,6 +244,16 @@
         return nullptr;
     }
 
+    Service* FindInterface(const std::string& interface_name) {
+        for (const auto& svc : services_) {
+            if (svc->interfaces().count(interface_name) > 0) {
+                return svc.get();
+            }
+        }
+
+        return nullptr;
+    }
+
     void DumpState() const;
 
     auto begin() const { return services_.begin(); }