c4goldsw and jan-kiszka Remove version check for pip
Was previously using / testing pip's "--root" option incorrectly (i.e. an empty
argument was supplied when doing non-root installations, or a relative path was
used), leading to a restriction of what version of pip we would allow (since it
pip would otherwise fail).  Use --root appropriately and remove version check
accordingly.

Signed-off-by: Chris Goldsworthy <christopher.goldsworthy@outlook.com>
[Jan: fixed ifneq syntax error, beautified PIP_ROOT assignment]
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Latest commit e42151c Jul 22, 2018