DHCP: Populate nameservers D-bus property from resolv.conf

Currently when DHCP enabled, nameservers D-bus property does not have
updated DHCP provided nameservers.

This commit populates nameservers D-bus property from resolv.conf

Tested By: verify nameservers D-bus property value with DHCP
enable/disable

Change DHCP server nameservers configuration & verify name servers
D-bus property updated on the interface.

Change-Id: If1a2508927d5f4f0c9c5d8b3f533fdf384d68821
Signed-off-by: Ravi Teja <raviteja28031990@gmail.com>
diff --git a/test/mock_ethernet_interface.hpp b/test/mock_ethernet_interface.hpp
index 8c12926..150cedd 100644
--- a/test/mock_ethernet_interface.hpp
+++ b/test/mock_ethernet_interface.hpp
@@ -16,7 +16,7 @@
     {}
 
     MOCK_METHOD((ServerList), getNTPServerFromTimeSyncd, (), (override));
-    MOCK_METHOD((ServerList), getNameServerFromResolvd, (), (override));
+    MOCK_METHOD((ServerList), getNameServerFromResolvd, (), (const override));
 };
 } // namespace network
 } // namespace phosphor