Change vsync to use more idiomatic err != nil style.
Change vsync to use more idiomatic err != nil style.

The change to the "if err != nil" style doesn't change any
functionality.

I also noticed that syncService.cancelAdvSyncbase is set, but
never called.  Added a call in Close.

Change-Id: I89190355735510a4d6298d8d2d26d4532fa8a85a

vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref,vanadium/go.ref