Fix CTS android.media package testEncodeVirtualDisplay fail on some device with low end processor

200ms are not enough to ensure the presentation to finish render for some devices
with low end process in such heavy system loading scenario.

The fix suggestion is: increase the thread sleep time from 200ms to 400ms for each color rendering.

Change-Id: I7f40c95a53613fb6be3324d5bbbf89a75a12be21
Signed-off-by: Hurri Lu <jlu32@marvell.com>