To avoid the JNI memory leaks in video editor codes

There is a protential memory leak in video editor JNI codes.
When importing so many video clips, the number of local reference
will exceed 512, which will cause the Dalvik virtual machine
crash. The patch will free each local reference when it's no
longer used to avoid memory leaks.

Change-Id: Iecd986c83f05a1103641746d6d43eef0a9c5ee40
Author: Wei Feng <wei.feng@intel.com>
Signed-off-by: Wei Feng <wei.feng@intel.com>
Singed-off-by: Shuo Gao <shuo.gao@intel.com>
Signed-off-by: Bruce Beare <bruce.j.beare@intel.com>
Signed-off-by: Jack Ren <jack.ren@intel.com>
Author-tracking-BZ: 40786