bridge: don't crash on bandwidth unplug with no bandwidth

If networkUnplugBandwidth is called on a network which has
no bandwidth defined, print a warning instead of crashing.

This can happen when destroying a domain with bandwidth if
bandwidth was removed from the network after the domain was
started.

https://bugzilla.redhat.com/show_bug.cgi?id=975359
(cherry picked from commit 658c932ab4aec2222b0ce3840a96748e73b39b3f)
Fix vPort management: FC vHBA creation

When creating a virtual FC HBA with virsh/libvirt API, an error message
will be returned: "error: Node device not found",
also the 'nodedev-dumpxml' shows wrong information of wwpn & wwnn
for the new created device.

Signed-off-by: xschen@tnsoft.com.cn

This reverts f90af69 which switched wwpn & wwwn in the wrong place.

https://www.kernel.org/doc/Documentation/scsi/scsi_fc_transport.txt
(cherry picked from commit 3c0d5e224c71cd85b123cd938eeb360502503cb0)