utils_net: raise a right error for bring down interface

Signed-off-by: Yanbing Du <ydu@redhat.com>
utils_test.libvirt: Fix a regex

In some case, interface may has no MAC address:
$virsh iface-list
Name                 State      MAC Address
--------------------------------------------
brlo                 inactive
eth0                 active     44:37:e6:4a:42:d1

So fix the regex to get empty MAC address.

Signed-off-by: Yanbing Du <ydu@redhat.com>
Modify secret-list and add net-update wrapper

1. Variable options is added twice in secret-list and keep the code
style simple and consistent with other APIs

2. Add net_update() API to support libvirt testcase virsh_net_update.py
Merge pull request #1626 from kylazhang/virsh-command

Modify secret-list and add net-update wrapper
virttest: fix compatibility with python2.4.

Signed-off-by: Jiří Župka <jzupka@redhat.com>
Merge pull request #1679 from jzupka/fix_compatibility_python24

virttest: fix compatibility with python2.4.
libvirt_vm: Fix wrong option --uri with -c.

Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
Merge pull request #1680 from yangdongsheng/libvirt_vm

libvirt_vm: Fix wrong option --uri with -c.
Merge pull request #1621 from will-Do/net_fix

Fix two  interface related problems