auto algo not working
Hi,

When I try to use the proxy with auto algo parameter, I have this error :

```
 * ABOUT        xmrig-proxy/5.0.0 gcc/5.4.0
 * LIBS         libuv/1.31.0 OpenSSL/1.1.1c
 * MODE         nicehash
 * POOL #1      pool.supportxmr.com:9000 algo auto
 * BIND #1      0.0.0.0:3333
 * BIND #2      [::]:3333
 * COMMANDS     hashrate, connections, verbose, workers
[2019-11-26 14:12:33.212] [pool.supportxmr.com:9000] unknown algorithm, make sure you set "algo" or "coin" option
[2019-11-26 14:12:33.212] [pool.supportxmr.com:9000] login error code: 6
```

I maked packets captures,

Proxy : 

`{"id":1,"jsonrpc":"2.0","method":"login","params":{"login":"*masked*","pass":"x","agent":"xmrig-proxy/5.0.0 (Linux x86_64) libuv/1.31.0 gcc/5.4.0"}}
{"id":1,"jsonrpc":"2.0","error":null,"result":{"id":"1f70f4ac-bcf6-4130-9a21-d771ab5cc9d0","job":{"blob":"0b0cbf84f4ee05b60d1342bfa72d6f37485a3e108ce26b0b66c6272392cdaeeee8976155ed35ac0000000066547d705c59ace198f392044621c4e4a194c10c3bd4b89f04705eb7bf149fa722","job_id":"BQk1LSklqDnMzo2ATmmeD/sGvJdR","target":"dc460300","id":"1f70f4ac-bcf6-4130-9a21-d771ab5cc9d0","height":1975320,"seed_hash":"00"},"status":"OK"}}

Client (direct) :

`{"id":1,"jsonrpc":"2.0","method":"login","params":{"login":"*masked*","pass":"x","agent":"XMRig/5.0.1 (Linux x86_64) libuv/1.31.0 gcc/5.4.0","algo":["cn/1","cn/2","cn/r","cn/fast","cn/half","cn/xao","cn/rto","cn/rwz","cn/zls","cn/double","cn/gpu","cn-lite/1","cn-heavy/0","cn-heavy/tube","cn-heavy/xhv","cn-pico","rx/0","rx/wow","rx/loki","rx/arq","argon2/chukwa","argon2/wrkz"]}}
{"id":1,"jsonrpc":"2.0","error":null,"result":{"id":"d39e5376-74ff-4c5b-9f14-358dc1e52f82","job":{"blob":"0b0cb486f4ee0576c8581347030b4b852b3696b1c003fc0b789e047c5b2e0e6d5e01506907ed3300000000bc5391cadd348c9975c87157bf48a8e57d74a2fb0ee373f83e6d9c2daafaebab1c","job_id":"nrC9MD+sn7dAe0XOkZNzMXfshSLm","target":"dc460300","id":"d39e5376-74ff-4c5b-9f14-358dc1e52f82","height":1975321,"seed_hash":"00","algo":"cn/r"},"status":"OK"}}
`
The proxy doesn't provide the algo support list, maybe it's the cause of problem.

Best regards.