sensorservice: Fix init sequence for pre-1.1 API sensor HALs

The sensors API introduced a new flush() method that older binaries
won't have. For those, replace the firstFlush invocation with a
setDelay call since a lot of implementations interpreted that as
the initialization step.
We also don't want any kind of call to flush() to happen when it
isn't there, since it'll either hit a random OEM extension or
a memory address we really don't want to execute.

Change-Id: I26ce923fe385751fed7d1c483a53c074249f0620
Revert "SensorEventQueue: Allow setRate on sensor enable"

This reverts commit 320fd662a3cf98c920fb9b2ae05e34c7ee3e623d. It's the wrong fix for the wrong problem. The main issue on
devices like the JF is the presence of a new method (flush) in the 1.1
sensor API, which can't be invoked in older blobs and should
be addressed in the sensorservice itself.

Change-Id: I2f5fff41db7a11ed2e0f6650d1f1cecb5e2a03fb