roachprod: fixup roachprod --sequential

[irfansharif]

..and the setting of cluster settings for single node clusters.
roachprod start --sequential was broken in #51329, and the broken-ness
outlined in TODOs in #51790. This PR just addresses those TODOs.

Fixes #51497
Fixes #51721
Fixes #51738
Fixes #51768
Fixes #51769
Fixes #51776

Release note: None

[cockroach-teamcity]

This change is 

[nvanbenschoten]

Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @irfansharif, @nvanbenschoten, and @petermattis)

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pkg/cmd/roachprod/install/cockroach.go, line 145 at r1 (raw file):

		// We reserve a few special operations like initializing the cluster,
		// and setting cluster settings, for node 1.

nit: no comma.

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pkg/cmd/roachprod/install/cockroach.go, line 475 at r1 (raw file):

	//    which prompts CRDB to auto-initialize. For nodes running >=20.1, we
	//    need to explicitly initialize.
	return !h.useStartSingleNode(vers) && nodes[nodeIdx] == 1 && vers.AtLeast(version.MustParse("v20.1.0"))

Do we want/need the nodes[nodeIdx] == 1 check?

[irfansharif]

thanks for the quick review!

bors r+

Reviewable status: complete! 0 of 0 LGTMs obtained (and 1 stale) (waiting on @petermattis)

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pkg/cmd/roachprod/install/cockroach.go, line 145 at r1 (raw file):

Previously, nvanbenschoten (Nathan VanBenschoten) wrote…

nit: no comma.

Done.

---

pkg/cmd/roachprod/install/cockroach.go, line 475 at r1 (raw file):

Previously, nvanbenschoten (Nathan VanBenschoten) wrote…

Do we want/need the nodes[nodeIdx] == 1 check?

Done. Inlined at caller.

[craig]

Build failed:

• GitHub CI (Cockroach)

[irfansharif]

✖ 1 test failed
FAILED TESTS:
  <TimeScaleDropdown>
    ✖ getTimeRangeTitle must return custom Title
      HeadlessChrome 83.0.4103 (Linux 0.0.0)
    AssertionError: expected 'Jul 24, 11:52PM -  12:02AM' to equal ' 11:52PM -  12:02AM'
        at Context.eval (webpack-internal:///./src/views/cluster/containers/timescale/timescale.spec.tsx:105:50)

UI test flake?

[irfansharif]

bors r+

[craig]

Build succeeded:

• GitHub CI (Cockroach)