This PR makes the modem_chat wait until a chat script chat
request has been sent before accepting responses to said
request.
This helps ensure that an unsolicitet response is not mistaken
for a response to a request, which is especially problematic
if the chat script chat is using an any match.
For example, start chat script sending AT+CGMI, expecting the
modem name as a response followed by OK
> start script, waiting for response immediately
> start sending "AT+CGMI"
> receive "+CEREG 1,0" while sending
> script accepts "+CEREG 1,0" as the response to "AT+CGMI"
> "AT+CGMI" sent
> receive "QUECTEL BG95"
> receive "OK"
script handler got "+CEREG 1,0" instead of "QUECTEL BG95"
After this PR:
> start script
> start sending AT+CGMI
> receive "+CEREG 1,0" while sending
> "AT+CGMI" sent
> start waiting for response
> receive "QUECTEL BG95"
> script accepts "QUECTEL BG95" as response to "AT+CGMI"
> receive "OK"
Signed-off-by: Bjarki Arge Andreasen <bjarki@arge-andreasen.me>