rootfs: correct file name parsing in case of version
rootfs: correct file name parsing in case of version

This patch corrects download file name parsing when it
tries to download specific version and date.

Change-Id: I5a45275ae26343e09e27ff18df9c3546b06ee023
Signed-off-by: Chanho Park <8ec285a53e21b773fd914e03c50e1b6431bc9aa8@samsung.com>

SamsungARTIK/build-artik