Commute EPICS_CA_ADDR_LIST in run.sh

Sometimes it's convenient to look at the machine on dev using our one way EPICS gateway. Right now `_op_api` calls `_epics_env` to apply the appropriate environment variables, but it would be nice if the user could supply their own addition to the env, e.g. 
```
bash etc/run.sh api -epics-env=$gateway
```
or the like.