Fix config drive mount and add flag to control the search order in which the driver retrieves instance metadata

[dgaponcic]

What this PR does / why we need it:
Currently the manila csi only uses metadata service to get instance metadata, which fails when using config drive.

• This PR adds a new flag --search-order (similar to cinder) to allow setting up the order in which the driver should try to retrieve the metadata. By default: configDrive,metadataService
• And this PR adds the missing bits to get the config drive to work.

Which issue this PR fixes(if applicable):
fixes #3118

Special notes for reviewers:

1. Start the node plugin without --search-order. It will use the default value of configDrive,metadataService. On a machine using metadata service, this is the output:

}
I0701 14:15:22.146174       1 driver.go:327] [ID:2] GRPC call: /csi.v1.Node/NodeGetInfo
...
I0701 14:15:22.146893       1 metadata.go:170] Attempting to mount configdrive on /tmp
I0701 14:15:22.148041       1 mount_linux.go:326] 'umount /tmp/kubelet-detect-safe-umount3371542402' failed with: exit status 1, output: umount: can't unmount /tmp/kubelet-detect-safe-umount3371542402: Invalid argument
...
E0701 14:15:22.148613       1 mount_linux.go:271] Mount failed: exit status 1


I0701 14:15:22.149110       1 metadata.go:204] Attempting to fetch metadata from http://169.254.169.254/openstack/latest/meta_data.json, ignoring proxy settings
I0701 14:15:22.288691       1 driver.go:333] [ID:2] GRPC response: {"node_id":"<node id>"}

It tried to mount the config drive, fails, and then tries the metadata service, which works.

2. Start the node plugin with --search-order=metadataService,configDrive. On an instance using config drive, this is the output:

I0701 14:47:56.211444       1 driver.go:327] [ID:2] GRPC call: /csi.v1.Node/NodeGetInfo
I0701 14:47:56.211462       1 driver.go:328] [ID:2] GRPC request: {}
I0701 14:47:56.211486       1 metadata.go:204] Attempting to fetch metadata from http://169.254.169.254/openstack/latest/meta_data.json, ignoring proxy settings

I0701 14:48:26.212841       1 metadata.go:170] Attempting to mount configdrive /dev/disk/by-label/config-2 on /tmp
...
I0701 14:48:26.216486       1 metadata.go:182] Configdrive mounted on /tmp
I0701 14:48:26.216921       1 mount_linux.go:401] Unmounting /tmp
I0701 14:48:26.218503       1 driver.go:333] [ID:2] GRPC response: {"node_id":"<node-id>"}

It tried to use the matadata sevice, and when it didn't work, tried the config drive, which worked.

Release note:

[manila-csi-plugin] Add `--search-order` flag to control the order in which instance metadata is retrieved (configDrive, metadataService)

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: dgaponcic / name: Diana Gaponcic (14b133e)

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[kubernetes-prow]

Hi @dgaponcic. Thanks for your PR.

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[gouthampacha]

/ok-to-test

@dgaponcic - have you signed the CLA?

[kayrus]

can you also adjust a corresponding helm chart template?

[kayrus]

please adjust docs accordingly

[kayrus]

thanks for the PR. Please set proper Release note in your initial message.