Agent's remote logger might deadlock agent

http://coin-master.ci.qt.io/coin/integration/qt/qt5/tasks/1596161503

http://coin.intra.qt.io/coin/integration/qt/qtbase/tasks/1596474709
https://qtmetrics.intra.qt.io/d/nOAsINmZz/jimis-telegraf-vms?orgId=1&from=1596475488955&to=1596478879195&var-server=1595996360-27491&var-inter=1s

In a rare case the agent logger might cause the agent to get deadlocked.

One possible reason is that agent's logger encounters something that it cannot handle or other ways deadlocks, after this the buffer for the running command fills and after this the command is unable to continue. This shows so that the remote logger is out of sync from the stdout on agent.