Telegraf failing to collect "ovs_dpctl" metric

[Giuseppe Petralia]

Telegraf is failing to collect ovs_dpctl metric.

This is happening on a jammy yoga ovn cloud with hw-offload enabled.

Openvswitch version is 2.17.3-0ubuntu0.22.04.2

telegraf run "ovs-appctl dpctl/show -s"

and it fails to parse the output with error:

```
Traceback (most recent call last):
  File "/var/lib/juju/agents/unit-telegraf-27/charm/files/telegraf_exec_metrics.py", line 627, in <module>
    main()
  File "/var/lib/juju/agents/unit-telegraf-27/charm/files/telegraf_exec_metrics.py", line 622, in main
    output = metric.parse(metric.get_input_content())
  File "/var/lib/juju/agents/unit-telegraf-27/charm/files/telegraf_exec_metrics.py", line 528, in parse
    datapath_entry[label] = self.parse_fields(rest.rstrip())
  File "/var/lib/juju/agents/unit-telegraf-27/charm/files/telegraf_exec_metrics.py", line 474, in parse_fields
    data[k] = self.parse_fields(v)
  File "/var/lib/juju/agents/unit-telegraf-27/charm/files/telegraf_exec_metrics.py", line 467, in parse_fields
    k, v = datapair.split(":")
ValueError: not enough values to unpack (expected 2, got 1)
```

Example of output that causes the error

```
# ovs-appctl dpctl/show -s
system@ovs-system:
  lookups: hit:2511988 missed:24068761 lost:0
  flows: 1
  masks: hit:26600554 total:1 hit/pkt:1.00
  cache: hit:2511695 hit-rate:9.45%
  caches:
    masks-cache: size:256
  port 0: ovs-system (internal)
    RX packets:0 errors:0 dropped:0 overruns:0 frame:0
    TX packets:0 errors:0 dropped:0 aborted:0 carrier:0
    collisions:0
    RX bytes:0 TX bytes:0
  port 1: genev_sys_6081 (geneve: packet_type=ptap)
    RX packets:0 errors:? dropped:? overruns:? frame:?
    TX packets:0 errors:? dropped:? aborted:? carrier:?
    collisions:?
    RX bytes:0 TX bytes:0
  port 2: br-int (internal)
    RX packets:0 errors:0 dropped:0 overruns:0 frame:0
    TX packets:0 errors:0 dropped:0 aborted:0 carrier:0
    collisions:0
    RX bytes:0 TX bytes:0
  port 3: br-data.3154 (internal)
    RX packets:37591 errors:0 dropped:0 overruns:0 frame:0
    TX packets:1174 errors:0 dropped:0 aborted:0 carrier:0
    collisions:0
    RX bytes:1637904 (1.6 MiB) TX bytes:49428 (48.3 KiB)
  port 4: br-data.3152 (internal)
    RX packets:1093169 errors:0 dropped:0 overruns:0 frame:0
    TX packets:204088 errors:0 dropped:0 aborted:0 carrier:0
    collisions:0
    RX bytes:60505164 (57.7 MiB) TX bytes:35780358 (34.1 MiB)
  port 5: br-data.3153 (internal)
    RX packets:519514 errors:0 dropped:0 overruns:0 frame:0
    TX packets:1187 errors:0 dropped:0 aborted:0 carrier:0
    collisions:0
    RX bytes:23026942 (22.0 MiB) TX bytes:49974 (48.8 KiB)
  port 6: br-data.3142 (internal)
    RX packets:2075073 errors:0 dropped:0 overruns:0 frame:0
    TX packets:149790 errors:0 dropped:0 aborted:0 carrier:0
    collisions:0
    RX bytes:113931726 (108.7 MiB) TX bytes:9561422 (9.1 MiB)
  port 7: br-data.3132 (internal)
    RX packets:1846249 errors:0 dropped:0 overruns:0 frame:0
    TX packets:149709 errors:0 dropped:0 aborted:0 carrier:0
    collisions:0
    RX bytes:104273166 (99.4 MiB) TX bytes:9555426 (9.1 MiB)
  port 8: br-data.3122 (internal)
    RX packets:3185682 errors:0 dropped:0 overruns:0 frame:0
    TX packets:242883 errors:0 dropped:0 aborted:0 carrier:0
    collisions:0
    RX bytes:183333500 (174.8 MiB) TX bytes:18445831 (17.6 MiB)
  port 9: br-data (internal)
    RX packets:22184858 errors:0 dropped:1 overruns:0 frame:0
    TX packets:3 errors:0 dropped:0 aborted:0 carrier:0
    collisions:0
    RX bytes:1188093087 (1.1 GiB) TX bytes:246
  port 10: bond0
    RX packets:7511164053 errors:0 dropped:0 overruns:0 frame:0
    TX packets:7073374556 errors:0 dropped:0 aborted:0 carrier:0
    collisions:0
    RX bytes:10147567794025 (9.2 TiB) TX bytes:8880013768200 (8.1 TiB)
```