Allow executing ODL test as many times as wanted on the same env

Allow executing ODL test as many times as wanted on the same env

Since the script add some lines to the file called __init__.robot
every time it executes, the next execution will add it again
which is unnecessary and it will fail.
This checks if those lines are already present and does nothing if so.

Change-Id: If4c2e10bcfcac0b7fde38ff213ea4ade4b83e4f1
Signed-off-by: jose.lausuch <jose.lausuch@ericsson.com>