selftests/user: move test out of Makefile into a shell script

Currently user copy test is run from the Makefile. Move it out
of the Makefile to be run from a shell script to allow the test
to be run as stand-alone test, in addition to allowing the test
run from a make target.

Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>