Port all available calls to libupdate_engine_client

This is as far as the port can go without improving the library itself.

Change-Id: I5d5dbf14b62746786364b2a7e1a9131d8ef7bfb1
Test: All affected commands still signal the daemon on dragonboard
Bug: 26233663
diff --git a/client_library/client_impl.h b/client_library/client_impl.h
index 912449f..c55f753 100644
--- a/client_library/client_impl.h
+++ b/client_library/client_impl.h
@@ -46,7 +46,8 @@
 
   bool ResetStatus() override;
 
-  bool SetTargetChannel(const std::string& target_channel) override;
+  bool SetTargetChannel(const std::string& target_channel,
+                        bool allow_powerwash) override;
 
   bool GetTargetChannel(std::string* out_channel) override;