Description of problem:
nmstate cannot create a vrf with mac or change the mac of an existed vrf device. Though we can use 'ip link add vrf0 address $mac' to create a vrf with specific mac address, we cannot change it once it was created.
Consider such a scenario: user created a vrf(vrf0), in order to use it next time, e.g. rebooting, saved it by running 'nmstatectl show vrf0 > backup.yml'. Next time user tries to recovery this vrf environment, it will fail if he runs 'nmstatectl set backup.yml' directly as in the transaction it contains a mac address.

Version-Release number of selected component (if applicable):
nmstate-0.4.1-1.el8.noarch

How reproducible:
100%

Steps to Reproduce:
echo "interfaces:
- name: vrf1
  type: vrf
  state: up
  mac-address: 72:B3:5C:B1:68:92
  vrf:
    route-table-id: 101" | nmstatectl set - #cannot create with mac

echo "interfaces:
- name: vrf1
  type: vrf
  state: up
  vrf:
    route-table-id: 101" | nmstatectl set -
nmstatectl show vrf1 # can see a random mac

echo "interfaces:
- name: vrf1
  type: vrf
  state: up
  mac-address: 72:B3:5C:B1:68:92
  vrf:
    route-table-id: 101" | nmstatectl set - #cannot change the mac

Actual results:
Traceback (most recent call last):
  File "/usr/bin/nmstatectl", line 11, in <module>
    load_entry_point('nmstate==0.4.1', 'console_scripts', 'nmstatectl')()
  File "/usr/lib/python3.6/site-packages/nmstatectl/nmstatectl.py", line 70, in main
    return args.func(args)
  File "/usr/lib/python3.6/site-packages/nmstatectl/nmstatectl.py", line 269, in apply
    args.save_to_disk,
  File "/usr/lib/python3.6/site-packages/nmstatectl/nmstatectl.py", line 309, in apply_state
    save_to_disk=save_to_disk,
  File "/usr/lib/python3.6/site-packages/libnmstate/netapplier.py", line 71, in apply
    _apply_ifaces_state(plugins, net_state, verify_change, save_to_disk)
  File "/usr/lib/python3.6/site-packages/libnmstate/netapplier.py", line 115, in _apply_ifaces_state
    _verify_change(plugins, net_state)
  File "/usr/lib/python3.6/site-packages/libnmstate/netapplier.py", line 120, in _verify_change
    net_state.verify(current_state)
  File "/usr/lib/python3.6/site-packages/libnmstate/net_state.py", line 63, in verify
    self._ifaces.verify(current_state.get(Interface.KEY))
  File "/usr/lib/python3.6/site-packages/libnmstate/ifaces/ifaces.py", line 443, in verify
    cur_iface.state_for_verify(),
libnmstate.error.NmstateVerificationError: 
desired
=======
---
name: vrf1
type: vrf
state: up
mac-address: 72:B3:5C:B1:68:92
vrf:
  route-table-id: 101

current
=======
---
name: vrf1
type: vrf
state: up
ipv4:
  enabled: false
ipv6:
  enabled: false
lldp:
  enabled: false
mac-address: 16:72:99:B7:5D:1A
mtu: 65536
vrf:
  port: []
  route-table-id: 101

difference
==========
--- desired
+++ current
@@ -2,6 +2,14 @@
 name: vrf1
 type: vrf
 state: up
-mac-address: 72:B3:5C:B1:68:92
+ipv4:
+  enabled: false
+ipv6:
+  enabled: false
+lldp:
+  enabled: false
+mac-address: 16:72:99:B7:5D:1A
+mtu: 65536
 vrf:
+  port: []
   route-table-id: 101


Expected results:
Ignore the mac address of vrf

Additional info: