Increase timeout for volume tests
Increase timeout for volume tests

Creating and deleting volumes is slow so tests like
test_list_volumes_pagination are often timing out

Change-Id: I87f59bdfb527326a2a90a03d524e38d632ea7377
Signed-off-by: Rosario Di Somma <73b2fe5f91895aea2b4d0e8942a5edf9f18fa897@dreamhost.com>

dtroyer/python-openstacksdk,openstack/python-openstacksdk,openstack-infra/shade,dtroyer/python-openstacksdk,openstack/python-openstacksdk,stackforge/python-openstacksdk,openstack-infra/shade,stackforge/python-openstacksdk