extract-utils: Fix handling of pulling src:dest pairs from dumps

Currently, the priority of the src and dest is inverted between
pulling from adb and pulling from a system dump.

Assume that we have a camera wrapper and write the proprietary-files.txt

lib/hw/camera.msm8996.so:lib/hw/camera.vendor.msm8996.so

If we pull from a phone running Lineage that has both files, we get

camera.vendor.msm8996.so

as the pulled blob.  If we take the exact same build and pull it
from the system dump (aka, your own $OUT directory that built the
installed software) you get

camera.msm8996.so

pull instead!

Make both paths follow the same logic so that you get the same
file independent of the source.

Change-Id: I479e0ae765339cc38fa05fcaad7943c528129463