:warning: check return err for customized agent install namespace

[qiujian16]

• check return err for customized agent install namespace

• Fix e2e

• Use default namespace if addon deployment config is not configured

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Summary

Related issue(s)

Fixes #

[openshift-ci[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: qiujian16

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[qiujian16]

/assign @zhujian7

[zhujian7]

/lgtm