Update decoding pattern to avoid possible assert in TinyCBOR

[jphickey]

Describe the bug
TinyCBOR may assert when decoding if it gets out of sync with the end of a container. This was discovered when attempting to decode an endpoint that used the "dtn" scheme as opposed to the "ipn" scheme. BPLib does not currently support the dtn scheme, and the internal decoding error flag was set as expected, but it still tried to "close" the container in the TinyCBOR state. This caused TinyCBOR to assert.

To Reproduce
Pass in a bundle from the CLA that uses a "dtn" scheme endpoint ID.

Expected behavior
Should not assert

Code snips
This is the line that asserted:

bplib/v7/src/v7_bp_container.c

Lines 104 to 110 in 3910733

	if (!cbor_value_at_end(&content))
	{
	dec->error = true;
	}
	/* return to parent scope */
	if (cbor_value_leave_container(parent, &content) != CborNoError)

In this case the dec->error flag was already set due to the decode issue, but the cbor_value_leave_container() is still called. This caused TinyCBOR to assert because it wasn't at the end of the container.

System observed on:
Debian with TinyCBOR 0.60

Additional context
The code must not make any additional calls into TinyCBOR once the error flag is set, as it will be out of sync.

Reporter Info
Joseph Hickey, Vantage Systems, Inc.