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/src/ethernet_interface.hpp b/src/ethernet_interface.hpp
index 0e9c536..7f3771e 100644
--- a/src/ethernet_interface.hpp
+++ b/src/ethernet_interface.hpp
@@ -170,6 +170,9 @@
      */
     ServerList staticNTPServers(ServerList value) override;
 
+    /** @brief Get value of nameservers */
+    ServerList nameservers() const override;
+
     /** @brief sets the Static DNS/nameservers.
      *  @param[in] value - vector of DNS servers.
      */
@@ -217,7 +220,7 @@
     /** @brief get the name server details from the network conf
      *
      */
-    virtual ServerList getNameServerFromResolvd();
+    virtual ServerList getNameServerFromResolvd() const;
 
     /** @brief Persistent sdbusplus DBus bus connection. */
     stdplus::PinnedRef<sdbusplus::bus_t> bus;