leveldb: Switch to using posix_fallocate()

:Release Notes:
The fallocate() system call fails when the database is on an NFS-mounted
or ext3 filesystem. posix_fallocate() doesn't suffer from this problem.

:Detailed Notes:
The commit also reverts https://g2g.palm.com/4180:
    7a101a4 leveldb: Fix for qemux86

:Testing Performed:
- Successfully booted with /var on NFS-mounted and ext3 filesystems.
- Ran MiniBAT.

:QA Notes:

:Issues Addressed:
[GF-55352] leveldb: fallocate() fails when database is on NFS-mounted
           filesystem
[GF-55423] CCC: leveldb=r4 (switch to using posix_fallocate)

Open-webOS-DCO-1.0-Signed-off-by: Iyad Qumei <iyad.qumei@lge.com>
Change-Id: I58d97573ce7f4515178f6bc1eb2c5fc502f6239d
Reviewed-on: https://g2g.palm.com/4202
Reviewed-by: DCO Verification
Tested-by: Herb Kuta <herb.kuta@lge.com>
Reviewed-by: Iyad Qumei <iyad.qumei@lge.com>
Tested-by: Iyad Qumei <iyad.qumei@lge.com>
Reviewed-by: Steve Lemke <steve.lemke@lge.com>
Tested-by: Steve Lemke <steve.lemke@lge.com>
Reviewed-by: Juhee Cho <juhee.cho@lge.com>
Tested-by: Juhee Cho <juhee.cho@lge.com>