Plugin loading ends with error when bool type from the cpolicy package is used

[katarzyna-z]

Plugin loading ends with error "loading plugin:
gob: type not registered for interface: cpolicy.BoolRule" when support for bool type from the cpolicy package is used.

I was trying to use support for bool type in the cpolicy package (added in #740) and I added something like this in GetConfigPolicy function for publisher plugin:

cp := cpolicy.New()
config := cpolicy.NewPolicyNode()

r1, err := cpolicy.NewBoolRule("test1", false)
handleErr(err)
r1.Description = "description"

config.Add(r1)
cp.Add([]string{""}, config)

[katarzyna-z]

I tested the fix and it works correctly. Thanks.