vbox: Resolve Coverity UNUSED_VALUE
vbox: Resolve Coverity UNUSED_VALUE

Handle a few places where Coverity complains about the value being
unused. For two of them (Close cases) - the comments above the close
indicate there is no harm to ignore the error - so added an ignore_value.
For the other condition, added an rc check like other callers.

Signed-off-by: John Ferlan <87558058f6f829e5ec976c8ef960720af4ff9c7d@redhat.com>

elmarco/libvirt,libvirt/libvirt,nertpinx/libvirt,taget/libvirt,olafhering/libvirt,libvirt/libvirt,jardasgit/libvirt,jardasgit/libvirt,jardasgit/libvirt,nertpinx/libvirt,libvirt/libvirt,eskultety/libvirt,andreabolognani/libvirt,olafhering/libvirt,datto/libvirt,crobinso/libvirt,datto/libvirt,rlaager/libvirt,jardasgit/libvirt,rlaager/libvirt,elmarco/libvirt,shugaoye/libvirt,datto/libvirt,zippy2/libvirt,rlaager/libvirt,agx/libvirt,agx/libvirt,zippy2/libvirt,zippy2/libvirt,jfehlig/libvirt,eskultety/libvirt,eskultety/libvirt,crobinso/libvirt,VenkatDatta/libvirt,VenkatDatta/libvirt,shugaoye/libvirt,nertpinx/libvirt,libvirt/libvirt,jfehlig/libvirt,olafhering/libvirt,agx/libvirt,andreabolognani/libvirt,shugaoye/libvirt,nertpinx/libvirt,crobinso/libvirt,andreabolognani/libvirt,jfehlig/libvirt,nertpinx/libvirt,datto/libvirt,eskultety/libvirt,VenkatDatta/libvirt,shugaoye/libvirt,taget/libvirt,elmarco/libvirt,agx/libvirt,eskultety/libvirt,olafhering/libvirt,VenkatDatta/libvirt,taget/libvirt,jfehlig/libvirt,datto/libvirt,fabianfreyer/libvirt,rlaager/libvirt,andreabolognani/libvirt,elmarco/libvirt,VenkatDatta/libvirt,fabianfreyer/libvirt,fabianfreyer/libvirt,fabianfreyer/libvirt,taget/libvirt,fabianfreyer/libvirt,shugaoye/libvirt,taget/libvirt,rlaager/libvirt,andreabolognani/libvirt,agx/libvirt,crobinso/libvirt,zippy2/libvirt,jardasgit/libvirt,elmarco/libvirt