Loving this tool so far! I recently ran into an issue where it seems that performing a Put or a Get operation against my local S3 bucket is collapsing XML-like structures. This in turn causes MD5 digest validation errors.

I have an S3 bucket...
```
aws --endpoint-url=http://localhost:4572 s3api create-bucket --bucket my-bucket
```

I start with a file called **test.xml**:
```
<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl"?>
<submission>
    <field1>fwefwefewfew</field1>
    <field2>fwefwefwe</field2>
    <field3>fefwefwe</field3>
</submission>
```

I then put this object into S3 using the following command:
```
 aws --endpoint-url=http://localhost:4572 s3api put-object --bucket my-bucket --key data/test1 --body test.xml
```

I'll grab the file back using the following command:
```
aws --endpoint-url=http://localhost:4572 s3api get-object --bucket my-bucket --key data/test1 test-back.xml
```

The file now looks like this:
```
<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl"?>
<submission><field1>fwefwefewfew</field1><field2>fwefwefwe</field2><field3>fefwefwe</field3></submission>
```

I found this while troubleshooting the following exception stack:
```
com.amazonaws.SdkClientException: Unable to verify integrity of data download.  Client calculated content hash didn't match hash calculated by Amazon S3.  The data may be corrupt.
	at com.amazonaws.services.s3.internal.DigestValidationInputStream.validateMD5Digest(DigestValidationInputStream.java:79)
	at com.amazonaws.services.s3.internal.DigestValidationInputStream.read(DigestValidationInputStream.java:61)
	at com.amazonaws.internal.SdkFilterInputStream.read(SdkFilterInputStream.java:72)
	at java.io.FilterInputStream.read(FilterInputStream.java:107)
	at com.amazonaws.util.IOUtils.toByteArray(IOUtils.java:44)
	at com.amazonaws.util.IOUtils.toString(IOUtils.java:58)
	at com.amazonaws.services.s3.AmazonS3Client.getObjectAsString(AmazonS3Client.java:1485)
```

I was able to work around this bug when I collapsed the XML structure myself prior to adding the file to S3. This is not ideal though.

Any ideas on why this is happening? I am using localstack version 0.8.8, installed with pip.

Thanks for any help!

bucket = 'test-bucket-%s' % short_uid()
        s3_client = aws_stack.connect_to_service('s3')
        s3_client.create_bucket(Bucket=bucket)
        s3_client.put_bucket_cors(
            Bucket=bucket,
            CORSConfiguration={
                'CORSRules': [{'AllowedMethods': ['GET', 'POST', 'PUT', 'DELETE'],
                               'AllowedOrigins': ['localhost']}]
            }
        )
        response = s3_client.get_bucket_cors(Bucket=bucket)
        self.assertEqual(response['ResponseMetadata']['HTTPStatusCode'], 200)
        
        s3_client.delete_bucket(Bucket=bucket)
    def test_s3_uppercase_names(self):
        
        bucket_name = 'TestBucket-%s' % short_uid()
        self.s3_client.create_bucket(Bucket=bucket_name)
        
        object_key = 'camelCaseKey'
        self.s3_client.put_object(Bucket=bucket_name, Key=object_key, Body='something')
        self.s3_client.get_object(Bucket=bucket_name, Key=object_key)
        self.assertRaises(Exception, self.s3_client.get_object, Bucket=bucket_name, Key=object_key.lower())
    def test_s3_get_response_headers(self):