AudioTrack: Fix timestamp startup condition

Suppress timestamps without valid kernel information or
a server update.

Update timing of server timestamp location to better indicate
when the server pull occurs.

Update write timing logic to suppress unneeded time calls
and to ensure proper throttling.

Bug: 28771691
Change-Id: I2cd25dad638ca1d0b1355d87d175d908f3bddb26
2 files changed