Add a create_router utility function

Similary to other neutron resources, add a utility function for
creating a logical router in tempest.api.network.base.BaseNetworkClient

Also, adapt test_floating_ips to use this function

Change-Id: I36f60028f75f7d4b2ed814a965431d2d4138cfbd
Partial-Bug: #1228091
add more test cases to api/network/security_groups

explicit rule parameters:
create a rule for each protocol (tcp, udp, icmp)

Change-Id: I5adc0d1f2af994031823e19675177566fb3db202
Merge "add more test cases to api/network/security_groups"
Merge "Add a create_router utility function"