region caching needs to take care cache invalidation

[balamurugana]

As the library caches bucket region, we would need to take care below cases

• if a bucket is deleted after the bucket gets cached, we would need to invalidate the cache if we get the request for the same bucket
• if a bucket is deleted and recreated after the bucket gets cached, we would need to invalidate the cache if we get region mismatch errors from amazon s3

[harshavardhana]

retry logic in this is needed for two cases and

• 400 Bad Request

<Error><Code>400 Bad Request</Code><Message>400 Bad Request</Message><BucketName>anythinglikenothing</BucketName><Key></Key><RequestId>10B1CB41110FF511</RequestId><HostId>6CfZYjQ1pUjINOsAszS29xrc/7y73Mb26GNCdizVauaUeZ4sAMQwusx/lTn2KI8p19HnM27ZqrM=</HostId><AmzBucketRegion>us-west-2</AmzBucketRegion></Error>

• AuthorizationHeaderMalformed

<Error><Code>AuthorizationHeaderMalformed</Code><Message>The authorization header is malformed; the region &#39;us-east-1&#39; is wrong; expecting &#39;us-west-2&#39;</Message><BucketName></BucketName><Key></Key><RequestId>1531B8C99ED42ACD</RequestId><HostId>47gvFpzOkdf9Kyr/G0mAvqCu55osRPtNjtYuIUPmm+yxXrjd+aIneNqukwhM1K0IOu3pG61+zCY=</HostId><AmzBucketRegion></AmzBucketRegion></Error>

[harshavardhana]

Keeping them here to remember.