frameworks/av: Fix for failure in CTS MediaRecorderTest cases

 -Issue: MediaRecorder CTS test cases are failing.

 -Root Cause: Running the CTS test "testRecorderRandomAction" at beginning
  sets the huge file size and stargeFrightRecorder set the 64 bit file
  offset.
  In MPEG4 writer estimateMoovBoxSize depends on a static const
  variable which uses this file offset info.
  As the variable to calculate estimateMoovBoxSize is static const it
  remains same for next media recording session even if file size is small.

 -Fix: Don't use static const variable which is used to calculate
  estimateMoovBoxSize as its value may change depending on file offsets.

Change-Id: I6bd859fcd7951a4e78abc50bc99dab38e8284877