Use pip module instead of pip itself

when the filepath is very long and pip is run in a
virtualenv, the filepath is truncated and the
commands don't work. Some ODL CSIT jobs have
this problem. They use the lftools to upload their
logs so these specific CSIT jobs are not getting
their logs updloaded.

Change-Id: I0b4c0ac785fe6e2fbd183c1b9332cc6fd7b0ecaa
Signed-off-by: Jamo Luhrsen <jluhrsen@redhat.com>