Avoid race conditions between DTMF and FLASH events
Signed-off-by: Oleksandr Remez oleksandr.remez@globallogic.com
Should be merged together with: https://dev.iopsys.eu/voice/libvoice-d2/-/merge_requests/10 https://dev.iopsys.eu/voice/libvoice-broadcom/-/merge_requests/16
Resolves the issue when cannot establish a three-way call because FLASH event is sent together with DTMF