We always send default flush timeout

When we send out config request, we always use flush timeout 0xffff
(infinity), which is the default value.

We don't need to include this value in config request.

Bug: 159815595
Tag: #refactor
Test: compile & verify basic functions working
Change-Id: Ic06f1e7e39ccbce2ec85c6126d30e179d5971837