fix cpu-overload during file transfer acceptance

TLS session was busy in handleStateEstablished()
during a data-transfer in "wait_host_acceptance" state.
Use a simple thread sleep instead of waitForData() to solve the issue.

Change-Id: I38b7a036863da950202597d52debbfff3329b875
Reviewed-by: Olivier Soldano <olivier.soldano@savoirfairelinux.com>