Static bucket can be repeatedly bound to bucketClaim

[FanZhang526]

Bug Report

What happened:
Static bucket can be repeatedly bound to bucketClaim, and bucket.spec.bucketClaim info will be updated after new bound.

What you expected to happen:
When a static bucket has been bound to a bucketClaim, another bucketClaim using this same static bucket should be failed.

How to reproduce this bug (as minimally and precisely as possible):
1、create a static bucket
2、create a bucketClaim by using this static bucket
3、create another bucketClaim by using same static bucket

Anything else relevant for this bug report?:

Environment:

• Kubernetes version (use kubectl version), please list client and server:
• Controller version (provide the release tag or commit hash):
• Provisoner name and version (provide the release tag or commit hash):
• Cloud provider or hardware configuration:
• OS (e.g: cat /etc/os-release):
• Kernel (e.g. uname -a):
• Install tools:
• Network plugin and version (if this is a network-related bug):
• Others: