virsh: Modify description for LIBVIRT_DEBUG=4 in manpage
virsh: Modify description for LIBVIRT_DEBUG=4 in manpage

As LIBVIRT_DEBUG=4 logs only error messages and there
are no levels above it, adjusting the description in
the man page accordingly.

Signed-off-by: Nitesh Konkar <0c76797a2b22fdb43818c29f9111edd281fa1e01@linux.vnet.ibm.com>

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