Add GATT busy checks

[tannewt]

I've triggered a bug where I'm sending multiple GATT operations at once. I'm doing an MTU exchange request and a discover services request at once. Other BLE stacks I've used will return a BUSY error for the second request. Nimble doesn't have these checks. Is this by design or would a PR be accepted to add these?

[rahult-github]

Hi @tannewt ,

Is this by design or would a PR be accepted to add these?

Since esp-nimble is taken from upstream mynewt nimble, request to please raise one PR upstream , so it can be taken up in all upcoming releases too going forward.

[tannewt]

Done! apache#1790