File writer size estimation improvement

o Do not count the reserved space for moov if the meta data size is small
o Do not count the extra 1KB disturbing small file estimation.
o Reduce the default minimum reserved space from 4 KB to 3 KB.
o Estimate the moov size based on both duration AND file size limit is set
  and set it to the smaller estimated value.

low risk change

bug - 3111983

Change-Id: I6ac2adb979d8cc12d6b4f1813d000c989add0199