fluentd total_limit_size sets value beyond available space

Description of problem:
When the `total_limit_size` for fluentd is configured according to the documentation.  Currently there is no restriction on this value. It can be set any large value even if space is not available on the disk. 

Version-Release number of selected component (if applicable):
5.2

How reproducible:
Steps to Reproduce:
1. Deploy cluster-logging
2. Set total_limit_size for fluentd
~~~~

1. oc edit ClusterLogging instance
   spec:
   forwarder:
   fluentd:
   buffer:
   totalLimitSize: 100G
   ~~~~

3. View logs
~~~~

Actual results:

• # oc logs fluentd-2zwx9 -c fluentd

Setting each total_size_limit for 3 buffers to 107374182400 bytes

Setting queued_chunks_limit_size for each buffer to 12800

Setting chunk_limit_size for each buffer to 8388608

Expected Results:

Setting each total_size_limit for 3 buffers to 6415029657 bytes

Setting queued_chunks_limit_size for each buffer to 764

Setting chunk_limit_size for each buffer to 8388608

Additional info: