fix: handle optional flags correctly in VRF route update

[ctreatma]

The test for the VRF route update subcommand was explicitly skipped. I added a helper function to wait for the VRF route to be ready before testing the update subcommand, but when the test was enabled it failed because the subcommand was not capable of updating tags without updating all other VRF route properties.

In addition to enabling the test for the VRF route update subcommand, this updates the subcommand itself so that it only updates a VRF route property if the user set the corresponding CLI flag.

Part of #414

[cprivitere]

Looks like the vrf-route-update-test is panicking after 30 seconds.

[displague]

There have been conversations about adding a --wait argument for create subcommands. The code used in testing could be surfaced as a feature in the future.

[ctreatma]

Looks like the vrf-route-update-test is panicking after 30 seconds.

I see a panic happening in a different test due to the test timeout being reached (~1000 seconds) and the VRF route update test failing because the route isn't ready in time. I triggered a re-run of the tests to see if the route update times out again. We may need to extend the test timeout (terraform uses 180m)

[cprivitere]

Tests are flakey but passing in general. The ones added in this PR pass and that's what matters.