qemuBlockJobRefreshJobs: Warn readers that 'job' may be invalid after update
qemuBlockJobRefreshJobs: Warn readers that 'job' may be invalid after update

Add a comment noting that job update can cause the pointer to be invalid
and thus should not be accessed after.

Signed-off-by: Peter Krempa <2cf5c04c61aa466e4a47bfedc747d17279c72ffc@redhat.com>
Reviewed-by: Pavel Mores <e8e79a41a9b826cd47122238a26f8527b5f610bc@redhat.com>
Reviewed-by: Michal Privoznik <83d82aaba2eed257f4814b0c239c260c4caaadf0@redhat.com>

fabianfreyer/libvirt,zippy2/libvirt,olafhering/libvirt,nertpinx/libvirt,crobinso/libvirt,fabianfreyer/libvirt,jfehlig/libvirt,libvirt/libvirt,olafhering/libvirt,jfehlig/libvirt,jardasgit/libvirt,jfehlig/libvirt,zippy2/libvirt,crobinso/libvirt,nertpinx/libvirt,libvirt/libvirt,jardasgit/libvirt,crobinso/libvirt,zippy2/libvirt,jardasgit/libvirt,nertpinx/libvirt,nertpinx/libvirt,zippy2/libvirt,crobinso/libvirt,olafhering/libvirt,fabianfreyer/libvirt,libvirt/libvirt,jardasgit/libvirt,jardasgit/libvirt,olafhering/libvirt,libvirt/libvirt,fabianfreyer/libvirt,fabianfreyer/libvirt,jfehlig/libvirt,nertpinx/libvirt