python3-nose: rename ${bindir}/nosetests into ${bindir}/nosetests3

python3-nose: rename ${bindir}/nosetests into ${bindir}/nosetests3

This resolves a conflict when both python-nose and python3-nose are pulled
into an image and try to install ${bindir}/nosetests binary.

This matches with how other distros are solving this problem, e.g. Debian:
https://packages.debian.org/jessie/all/python3-nose/filelist

Also, other packages like python3-setuptools are already doing the same with
their binaries.

Signed-off-by: Denys Dmytriyenko <denys@ti.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>