Some memobjs (e.g. devobj) will not be considered 'in memobj' by
page_is_in_memobj.
Instead of trying to play whack-a-mole with the non-fileobj memobjs,
base the copy check on range's memobj and VR_PRIVATE (do not copy
MAP_SHARED mappings, so the fault handler will do the right thing™
when required)
Change-Id: Ic32cdc7766754f6559753b34845eb8c5cff6ed13
Refs: #1255