Error when trying to update S3 binary field

## Gentics Mesh Version, operating system, or hardware.
- v1.7.x

## Operating System
- Linux
- MacOSX
- Windows

## JVM
- Oracle JDK 1.8.0_100
- Open JDK 1.8.0_100

## Problem
When trying to replace a file in S3 using the upload endpoint, a duplicated key exception is thrown.

## Reproducer
In S3 Upload Handler, if the code is modified to create two s3 binaries instead of one inside the tx, a **ORecordDuplicatedException** is thrown.

## Expected behaviour
There should be only one S3 Binary for a specific objectKey and there shouldn't be duplicated records.

## Actual behaviour
There can be more than one created S3 Binary Field with the same objectKey.