libxl: Resolve Coverity CHECKED_RETURN
libxl: Resolve Coverity CHECKED_RETURN

Periodically my Coverity scan will return a checked_return failure
for libxlDomainShutdownThread call to libxlDomainStart. Followed the
libxlAutostartDomain example in order to check the status, emit a
message, and continue on.

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