StageFright: SampleTable sync sample search procedure correction

There was a problem with calculation of closest sample in sample table:
it didn't return the closest sample, but always the next one.
This patch corrects this by adjusting this value to the closest,
as it should be.

Change-Id: Ie8fcdcde8754243f6db5d14830e394667b94a9b1
Signed-off-by: Dmytro Dubovyk <dmytro.dubovyk@ti.com>
findSyncSampleNear returns incorrect sample

SampleTable::findSyncSampleNear does not return the closest
sync sample but rather the next one after it.

As a result, for some videos it is not possible to seek backwards
using the rewind button in the player. And the seekbar does
not select the closest point matching the seek operation.

This fix modifies SampleTable::findSyncSampleNear to return
the closest sample.

Change-Id: I11bdc19435004cff904c4b4b7a9ad8af1d7dff83

Conflicts:
	media/libstagefright/SampleTable.cpp