Occasional json corruption on stratum receive
### Description
 
Occasional JSON corruption on stratum receive
 
### Steps to Reproduce
 
Running the pool on x16r algo, couldn't reproduce solo but occurs on our pool of ~20 miners
 
### Expected behavior
 
Normal JSON, not occasionally corrupted JSON
 
### Actual behavior
 
Thee server console shows errors about invalid JSON from various handlers
 
### Reproduces how often
 
Every few minutes, and immediately after miners reconnect after a pool restart
 
### Version
 
Latest master branch at commit df1348e
 
### Additional Information
 
An example error is
 
> [2018-05-19 00:45:44.3500] [E] [RVNS] [Pool] [0HLDSNJ4LNTJF] Connection json error state: Unexpected character encountered while parsing value: . Path '', line 0, position 0.
> [2018-05-19 00:45:44.3500] [E] [RVNS] [Pool] [0HLDSNJ4LNTJF] Received request data: 
> [2018-05-19 00:45:44.3500] [E] [RVNS] [Pool] [0HLDSNJ4LNTJF] Connection json error state: Unexpected character encountered while parsing value: �. Path '', line 0, position 0.
> [2018-05-19 00:45:44.3500] [E] [RVNS] [Pool] [0HLDSNJ4LNTJF] Received request data: �Z����
> [2018-05-19 00:45:44.3500] [E] [RVNS] [Pool] [0HLDSNJ4LNTJF] Connection json error state: Unexpected character encountered while parsing value: ߽. Path '', line 0, position 0.
> [2018-05-19 00:45:44.3500] [E] [RVNS] [Pool] [0HLDSNJ4LNTJF] Received request data: 
> �Z����
> ߽�߽�t", "params": ["redacted", "00001241", "00000000", "5aff73a6", "ddc
 
We ran WireShark to capture the exact packets which the server was receiving over the network and the data is 100% being received correctly as completely valid json, and it's being corrupted some point after that