config InitDefaults

[michel-laterman]

go-ucfg's Unpack method calls InitDefaults on the passed item along with any of it's children that implement the function.

However we explicity call the children's InitDefaults from the parent:

fleet-server/internal/pkg/config/input.go

Lines 155 to 160 in 0718a55

	func (c *Input) InitDefaults() {
	c.Type = fleetInputType
	c.Server.InitDefaults()
	c.Cache.InitDefaults()
	c.Monitor.InitDefaults()
	}

and this continues for a few extra layers:

fleet-server/internal/pkg/config/input.go

Lines 96 to 109 in 0718a55

	func (c *Server) InitDefaults() {
	c.Host = kDefaultHost
	c.Port = kDefaultPort
	c.InternalPort = kDefaultInternalPort
	c.Timeouts.InitDefaults()
	c.CompressionLevel = flate.BestSpeed
	c.CompressionThresh = 1024
	c.Profiler.InitDefaults()
	c.Limits.InitDefaults()
	c.Runtime.InitDefaults()
	c.Bulk.InitDefaults()
	c.GC.InitDefaults()
	c.PGP.InitDefaults()
	}

These extra InitDefaults calls are not needed; the input's InitDefaults can probably be reduced to

func (c *Input) InitDefaults() { 
 	c.Type = fleetInputType 
}

and most other structs in our config package can be redone as well.
We should try to clean this up to reduce extra calls.