Increase timeout for py26/27 unit tests

The current trunk of neutron already runs
very close to the time limit so now jobs
fail due to timeout sporadically. This increases
the limit by 10 minutes to mitigate the problem
until the unit tests can be deduplicated.

Change-Id: I86f088035819ec454c418ac3f9a9478a255156b1
Closes-Bug: #1294715
Merge "Increase timeout for py26/27 unit tests"