fix issue#526

[shaoyongfeng]

What this PR does / why we need it: In order to run aliyun cmd via gardenctl, we need arguments after aliyun key word and pass to aliyun cli. but aliyun key word is duplicated in this case which causes error when running any aliyun cmd.

Which issue(s) this PR fixes: Fixes #526

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Release note:

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[gardener-robot]

@shaoyongfeng Thank you for your contribution.