Jira 769 CurieBLE: cannot discover characteristics in 0x1800 and 0x1801 services

I'm using the peripheral explorer with [bleno's echo example](https://github.com/sandeepmistry/bleno/tree/master/examples/echo), it doesn't report any characteristics in the 0x1800 and 0x1801 services.

Here's the output:

```
BLE Central - Peripheral Explorer
Found C8:69:CD:41:84:A2 ''
Found 00:19:0E:11:24:06 '' ec00
Connecting ...
Connected
Discovering attributes ...
Attributes discovered

Device name:
Service 1800
Service 1801
Service ec00
Characteristic ec0e, properties 0x26

Disconnecting ...
Disconnected

```

Reproduce the peripheral explorer report with bleno's echo example and compare discovery of services 0x1800, 0x1801, and ec00. Start at the explorer's attribute-discovery path; done means determining why characteristics are absent from 0x1800 and 0x1801 and adding a verified fix or documenting the expected behavior.

Written by the indexing model from the issue text.