Sample index in stsc is bigger than samplecount in stsz

When sample index in stsc is bigger than samplecount in stsz,
it returns error and video playing stops. Solution is to
align samplecount in stsz.

Bug: 122746529
Test: Play the file whose sample index in stsc box is bigger
than samplecount in stsz box and check if it can play normally

Change-Id: I2f09d6d17ff6bd04df076d744a25094c12524f19