Avoid leaking cursors

Adding try/finally blocks to make sure that cursor
resources are let go

Change-Id: I596074aa9ab5752f91a26b5a03e1f39c23c64a5f
Add support to continue download when HTTP response etag is empty

As per AOSP behaviour application download can not resume when
HTTP response header contains empty etag.

Add fake Etag to support continue download in HTTP server
response header.

Change-Id: Iea7a51b3ada04cffe5f15253dbf3bec038d7146d
CRs-Fixed: 623780
Merge "Avoid leaking cursors" into kitkat
Merge "Add support to continue download when HTTP response etag is empty" into kitkat