Automatically load kernel module dependencies

Before this commit, you'd have to manually insert the kernel module for
OVS or OF kernel modules, and you couldn't run one regression test with
all 3.

Now, these are kmod insert/remove is handled automatically.

mininet/test/test_nets.py

@@ -7,10 +7,13 @@ import unittest
 
 from mininet.net import init, Mininet
 from mininet.node import KernelSwitch, Host, Controller, ControllerParams
+from mininet.node import UserSwitch, OVSKernelSwitch
 from mininet.topo import SingleSwitchTopo, LinearTopo
 
 # temporary, until user-space side is tested
-SWITCHES = { 'kernel': KernelSwitch }
+SWITCHES = { 'kernel': KernelSwitch,
+             'user': UserSwitch,
+             'ovsk': OVSKernelSwitch }
 
 
 class testSingleSwitch( unittest.TestCase ):