* cmd: fix cli when admin endpoint uses new unix socket permission format
Fixes a bug where the following Caddyfile
```Caddyfile
{
admin unix/admin.sock|0660
}
```
and `caddy reload --config Caddyfile`
would throw the following error instead of reloading it:
```
INFO using provided configuration {"config_file": "Caddyfile", "config_adapter": ""}
Error: sending configuration to instance: performing request: Post "http://127.0.0.1/load": dial unix admin.sock|0660: connect: no such file or directory
[ERROR] exit status 1
```
---
This bug also affected `caddy start` and `caddy stop`.
* Move splitter function to internal
---------
Co-authored-by: Matthew Holt <mholt@users.noreply.github.com>
Emily