Only skip operation on snapshot partitions

On Virtual A/B devices, don't skip SOURCE_COPY on
static partitions.

Test: update_engine_unittest
Test: incremental update to self
Change-Id: I5c93b501e09f50f559151eb77d83052373c90d0d
diff --git a/common/dynamic_partition_control_stub.cc b/common/dynamic_partition_control_stub.cc
index 06f6b3c..bc792c8 100644
--- a/common/dynamic_partition_control_stub.cc
+++ b/common/dynamic_partition_control_stub.cc
@@ -33,7 +33,7 @@
 }
 
 bool DynamicPartitionControlStub::ShouldSkipOperation(
-    const InstallOperation& operation) {
+    const std::string& partition_name, const InstallOperation& operation) {
   return false;
 }