Some regtest tests depend on manual fee injection to simulate certain
mempool conditions (e.g. lnwatcher_waits_until_fees_go_down). This is
done by manually injecting fee estimates into the `Network` object using
the `test_inject_fee_etas` cli command. However it can still happen that
the Network automatically updates its fee estimates from the connected
electrum server in the time between injecting the fee and the actual
tested logic making decisions based on the fee. This causes the test to
fail sometimes.
By setting the `test_disable_automatic_fee_eta_update` true the Network
will stop automatically updating the fee estimates and the test will
behave as expected.