Backend changes for Populating Nameservers(DNS & Static)

- As per the proposed design :
https://lists.ozlabs.org/pipermail/openbmc/2019-September/018399.html

Depends on :
https://gerrit.openbmc-project.xyz/#/c/openbmc/phosphor-dbus-interfaces/+/26060/

The idea of this commit is to

- Support NameServers(Read Only) property to display current
  Nameservers (both DHCP provided& Static) configured on the
  interface.

- Support StaticNameServers(Writable) property by which user
  can set the Nameservers on an interface.

Tested By:

1.Configure a DNS via DHCP Server & Make sure NameServer property
  populates accordingly.
2.With DNS from DHCP existing, set a name server using PATCH on
  StaticNameServer property & make sure both properties populate
  the data as per the proposal.
3.Make sure /etc/resolv.conf is populated with the right content
  in case of DHCP/Static and DHCP & Static (Co-existing)
4.Make sure network configuration file is updated properly when
  user sets a staic name server.

Signed-off-by: Manojkiran Eda <manojkiran.eda@gmail.com>
Change-Id: If10b9aa683d2b50e51780e91323c6d10a5ec3710
diff --git a/test/test_network_manager.cpp b/test/test_network_manager.cpp
index 64ca87d..7943057 100644
--- a/test/test_network_manager.cpp
+++ b/test/test_network_manager.cpp
@@ -27,7 +27,7 @@
 {
   public:
     sdbusplus::bus::bus bus;
-    Manager manager;
+    MockManager manager;
     std::string confDir;
     TestNetworkManager() :
         bus(sdbusplus::bus::new_default()),
@@ -63,7 +63,6 @@
     using namespace sdbusplus::xyz::openbmc_project::Common::Error;
     EXPECT_THROW(createInterfaces(), InternalFailure);
 }
-
 // getifaddrs returns single interface.
 TEST_F(TestNetworkManager, WithSingleInterface)
 {
@@ -96,6 +95,5 @@
     EXPECT_EQ(true, manager.hasInterface("igb0"));
     EXPECT_EQ(true, manager.hasInterface("igb1"));
 }
-
 } // namespace network
 } // namespace phosphor