Virtlet diagnostics

[ivan4th]

This adds a possibility to retrieve Virtlet diagnostics information using sonobuoy or virtletctl. When using sonobuoy, a plugin is added that uses virtlet image to invoke virtletctl diag.
virtletctl dumpmetadata command is removed as its output is now available as part
of what virtletctl diag dump produces, but it's obtained in a safer manner.

• diagnostics framework (collecting info, unpacking info from JSON to files&dirs)
• command-based diagnostics (ip r etc.)
• collecting qemu log files
• dumping Go stack
• examining network namespaces
• dumping metadata info
• dumping libvirt xml info
• virtlet --diag (grabbing diagnostics info from within the Virtlet pod)
• add virtletctl diag dump that retrieves diagnostics info from each virtlet pod (--json to get raw json w/o unpacking)
• add virtletctl diag unpack that unpacks Virtlet diagnostics from JSON file
• add virtletctl diag sonobuoy that patches sonobuoy yaml to inject Virtlet plugin
• retrieve virtlet pod logs during virtletctl diag dump [convenience]
• retrieve criproxy logs on the node, if found [convenience]
• fix CodeClimate issues
• remove virtletctl dumpmetadata
• add docs

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This change is 

[ivan4th]

The PR is ready for review.

[jellonek]

Please remove from PR changes in docs which are only changing timestamp.

Reviewed 43 of 50 files at r1, 1 of 1 files at r2.
Reviewable status: 0 of 2 LGTMs obtained

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docs/diagnostics.md, line 6 at r2 (raw file):

[virtletctl diag](virtletctl/virtletctl_diag.md) commands that can
help with troubleshooting. The diagnostics can be invoked either
directly or buy means of a

s/buy/by/

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pkg/diag/diag.go, line 109 at r2 (raw file):

	switch {
	case dr.Name == "":
		return errors.New("Result name is not set")

error message should started from lower case character.

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pkg/diag/diag.go, line 114 at r2 (raw file):

		return nil
	case !dr.IsDir && len(dr.Children) != 0:
		return errors.New("Result can't contain both Data and Children")

same as above

[ivan4th]

As of the timestamps, I re-generated docs several times in different commits. I'm not sure filtering each commit or adding another one on top of them to revert the changes is worth it ;(

Reviewable status: 0 of 2 LGTMs obtained

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docs/diagnostics.md, line 6 at r2 (raw file):

Previously, jellonek (Piotr Skamruk) wrote…

s/buy/by/

Done.

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pkg/diag/diag.go, line 109 at r2 (raw file):

Previously, jellonek (Piotr Skamruk) wrote…

error message should started from lower case character.

This is a message that reports a malformed data structure. The structure is called Result (starting from capital letter). This error shouldn't happen under normal circumstances, so it's kind of "internal"

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pkg/diag/diag.go, line 114 at r2 (raw file):

Previously, jellonek (Piotr Skamruk) wrote…

same as above

same, capitalized Result is the name of the structure

[jellonek]

Reviewable status: 0 of 2 LGTMs obtained, and 1 stale

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pkg/diag/diag.go, line 109 at r2 (raw file):

Previously, ivan4th (Ivan Shvedunov) wrote…

This is a message that reports a malformed data structure. The structure is called Result (starting from capital letter). This error shouldn't happen under normal circumstances, so it's kind of "internal"

Ah, right. My mistake.

[lukaszo]

Reviewable status: 1 of 2 LGTMs obtained, and 1 stale