Bug 1817948

Description of problem:
When creating bond via cockpit, in the "Bond Settings" page, the default value for "Mode" drop-down list is "Active backup". If keep this default value, in the generated bond, the bond mode is "Round Robin".

Version-Release number of selected component (if applicable):
cockpit-system-211.3-1.el8.noarch
cockpit-ws-211.3-1.el8.x86_64
cockpit-ovirt-dashboard-0.14.3-1.el8ev.noarch
cockpit-211.3-1.el8.x86_64
cockpit-bridge-211.3-1.el8.x86_64
cockpit-dashboard-211.3-1.el8.noarch
cockpit-storaged-211.3-1.el8.noarch

How reproducible:
100%

Steps to Reproduce:
1. Install "redhat-virtualization-host-4.4.0-20200325.0.el8_2"
2. Login to cockpit
3. Click "Networking" -> "Add Bond", in the "Bond Settings" page, select 2 NICs from the "Interfaces" check-box
4. Keep the default value of "Mode" as "Active backup", click the "Apply" button
5. Enter "Networking" -> "bond0" page, focus on the value of the "Bond" item in bond0
6. Login RHVH, check the configuration file "ifcfg-bond0"
   # cat /etc/sysconfig/network-scripts/ifcfg-bond0


Actual results:
In the "Networking" -> "bond0" page, the value of "Bond" is "Round Robin" and in the generated "ifcfg-bond0" file, the mode is "balance-rr"
~~~
BONDING_OPTS="downdelay=0 miimon=100 mode=balance-rr updelay=0"
TYPE=Bond
BONDING_MASTER=yes
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=dhcp
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV6INIT=yes
IPV6_AUTOCONF=yes
IPV6_DEFROUTE=yes
IPV6_FAILURE_FATAL=no
IPV6_ADDR_GEN_MODE=stable-privacy
NAME=bond0
UUID=a42cb335-2b3b-4c7c-8212-421f2000dbc4
DEVICE=bond0
ONBOOT=yes
AUTOCONNECT_SLAVES=yes
~~~

Expected results:
In the "Bond Settings" page, if the default value of "Mode" is "Active backup", the "Primary" drop-down list should be visible by default and the created bond mode should be "Active backup"

Additional info:
In the "Bond Settings" page, from the "Mode" drop-down list, if select an other mode before clicking the "Active Backup" mode, then click the "Active backup" mode, the result will be correct.