VPP nat44 and cgnat should be mutually exclusive
To reproduce:
```
set interfaces ethernet eth1 address '100.64.0.1/24'
set vpp settings interface eth1
set vpp settings interface eth3
set vpp nat cgnat interface inside 'eth1'
set vpp nat cgnat interface outside 'eth3'
set vpp nat cgnat rule 100 inside-prefix '100.64.0.0/24'
set vpp nat cgnat rule 100 outside-prefix '192.0.2.0/30'
commit
set vpp nat nat44 address-pool translation address 192.0.2.0-1.8.2.1
set vpp nat nat44 interface inside eth1
set vpp nat nat44 interface outside eth3
commit
```
After the second commit:
```
vyos@r14# commit
[ vpp nat nat44 ]
Traceback (most recent call last):
File "/usr/libexec/vyos/services/vyos-configd", line 157, in run_script
script.apply(c)
File "/usr/libexec/vyos/conf_mode/vpp_nat_nat44.py", line 456, in apply
n.add_nat44_address_range(address, twice_nat=False)
File "/usr/lib/python3/dist-packages/vyos/vpp/nat/nat44.py", line 98, in add_nat44_address_range
self.vpp.api.nat44_add_del_address_range(
File "/usr/lib/python3/dist-packages/vpp_papi/vpp_papi.py", line 130, in __call__
return self._func(**kwargs)
^^^^^^^^^^^^^^^^^^^^
File "/usr/lib/python3/dist-packages/vpp_papi/vpp_papi.py", line 565, in f
return self._call_vpp(i, msg, multipart, **kwargs)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/usr/lib/python3/dist-packages/vpp_papi/vpp_papi.py", line 854, in _call_vpp
raise VPPIOError(2, "VPP API client: read failed")
vpp_papi.vpp_papi.VPPIOError: [Errno 2] VPP API client: read failed
[[vpp nat nat44]] failed
Commit failed
[edit]
vyos@r14#
```