Don't return error in case one of a seed down

[ahmadhamzh]

What this PR does / why we need it:
in case of error come when fetching clusters from seed don't return the error and keep fetching clusters from other seeds

Which issue(s) this PR fixes:
Fixes #6056

What type of PR is this?
/kind bug

Fix issue with managing clusters if some seeds are down. 

NONE

[ahmadhamzh]

/retest

[ahmedwaleedmalik]

/retest

[ahmedwaleedmalik]

/approve

[kubermatic-bot]

LGTM label has been added.

Git tree hash: 823312ad102b526a697a0f62b306a334669120f7

[kubermatic-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ahmedwaleedmalik

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Needs approval from an approver in each of these files:

• modules/api/pkg/handler/OWNERS [ahmedwaleedmalik]
• modules/api/pkg/provider/kubernetes/OWNERS [ahmedwaleedmalik]
• modules/web/src/OWNERS [ahmedwaleedmalik]

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[ahmedwaleedmalik]

/cherry-pick release/v2.23

[kubermatic-bot]

@ahmedwaleedmalik: once the present PR merges, I will cherry-pick it on top of release/v2.23 in a new PR and assign it to you.

In response to this:

/cherry-pick release/v2.23

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[ahmedwaleedmalik]

/cherry-pick release/v2.22

[kubermatic-bot]

@ahmedwaleedmalik: once the present PR merges, I will cherry-pick it on top of release/v2.22 in a new PR and assign it to you.

In response to this:

/cherry-pick release/v2.22

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[kubermatic-bot]

@ahmedwaleedmalik: new pull request created: #6381

In response to this:

/cherry-pick release/v2.23

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[kubermatic-bot]

@ahmedwaleedmalik: #6374 failed to apply on top of branch "release/v2.22":

Applying: don't return error in case of seed down
Using index info to reconstruct a base tree...
M	modules/api/pkg/handler/v1/project/project.go
M	modules/api/pkg/handler/v2/cluster/cluster.go
M	modules/web/src/app/core/services/cluster.ts
Falling back to patching base and 3-way merge...
Auto-merging modules/web/src/app/core/services/cluster.ts
Auto-merging modules/api/pkg/handler/v2/cluster/cluster.go
CONFLICT (content): Merge conflict in modules/api/pkg/handler/v2/cluster/cluster.go
Auto-merging modules/api/pkg/handler/v1/project/project.go
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
Patch failed at 0001 don't return error in case of seed down
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".

In response to this:

/cherry-pick release/v2.22

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[ahmedwaleedmalik]

/cherry-pick release/v2.22

Backport for 2.22 is not required anyways.