Aligned Nameservers property with Redfish Spec

- As per the below mentioned proposal,i have added a new
  property StaticNameServers & also modified the definition
  of the existing Nameservers property

https://lists.ozlabs.org/pipermail/openbmc/2019-September/018399.html

- As mentioned in the proposal:

[x] Nameservers - will now be only a readonly Property, and it
                  contains all the DNS servers(Static & Dynamic)
	          configured on the interface.
- This should support NotAllowed Error, so that if a user tries
  to patch this property,it returns operation NotAllowed as status.

[x] StaticNameServers - will be a writable property,which user can
			patch with a list of IP address(s).
- This should support InvalidArgument Error, so that if user tries
  to patch with some junk data, we can return InvalidArgument when
  the backend validation fails.

Signed-off-by: Manojkiran Eda <manojkiran.eda@gmail.com>
Change-Id: I3d85463c7e37daf9f98f1f35f4efeaeb52714291
1 file changed