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/net.py

@@ -151,6 +151,8 @@ class Mininet( object ):
         self.dps = 0 # number of created kernel datapaths
         self.terms = [] # list of spawned xterm processes
 
+        switch.setup()
+
         if build:
             self.build()