thrift response error: unknown field type 108 using thrift_proxy

*Title*: thrift response error: unknown field type 108 using thrift_proxy

*Description*:
We have a service with Thrift RPC interface. When using thrift_proxy while most requests were successful. There were numerous errors with `thrift response error: unknown field type 108` and the field type number has several possible values such as 108, 111, -105 etc. There were no such errors when connecting to the service directly.

*Config*:
```
admin:
access_log_path: /tmp/admin_access.log
address:
socket_address:
protocol: TCP
address: 0.0.0.0
port_value: 9901
static_resources:
listeners:
- address:
socket_address:
protocol: TCP
address: 0.0.0.0
port_value: 12000
filter_chains:
- filters:
- name: envoy.filters.network.thrift_proxy
config:
transport: AUTO_TRANSPORT
protocol: BINARY
stat_prefix: 'thrift_svc'
thrift_filters:
- name: envoy.filters.thrift.router
route_config:
routes:
- match:
method_name: ''
route:
cluster: thrift_svc
clusters:
- name: thrift_svc
connect_timeout: 0.25s
type: LOGICAL_DNS
lb_policy: ROUND_ROBIN
extension_protocol_options:
envoy.filters.network.thrift_proxy:
transport: FRAMED
protocol: TWITTER
health_checks:
- interval: 10s
timeout: 3s
unhealthy_threshold: 2
healthy_threshold: 1
tcp_health_check: {}
load_assignment:
cluster_name: thrift_svc
endpoints:
- lb_endpoints:
- endpoint:
address:
socket_address:
address: 'thrift-svc'
port_value: 5908
```

*Logs*:
```
[2019-07-20 20:09:48.590][11][error][thrift] [source/extensions/filters/network/thrift_proxy/conn_manager.cc:653] [C11] thrift response error: unknown field type 108
[2019-07-20 20:11:42.505][16][error][thrift] [source/extensions/filters/network/thrift_proxy/conn_manager.cc:653] [C64] thrift response error: unknown field type 108
[2019-07-20 20:11:44.725][16][error][thrift] [source/extensions/filters/network/thrift_proxy/conn_manager.cc:653] [C66] thrift response error: unknown field type 111
[2019-07-20 20:11:56.267][16][error][thrift] [source/extensions/filters/network/thrift_proxy/conn_manager.cc:653] [C76] thrift response error: unknown field type 111
[2019-07-20 20:16:51.869][13][error][thrift] [source/extensions/filters/network/thrift_proxy/conn_manager.cc:653] [C116] thrift response error: unknown field type 108
```