Update persist.sys.usb.config on runtime

persist.sys.usb.config values can't be combined on build-time when
property files are split into each partition.
So we need to apply the same rule of
build/make/tools/post_process_props.py on runtime.

Test: building succeeded and tested on sailfish.
Bug: 37617113
Bug: 37648659

Change-Id: I78cdffee446d3ae6a89f138faed5f3149e4b507d