config_parser: Reduce number of file reads

This changes focuses on reducing the number of Parser() constructions to
limit the number of duplicate file reads.

Change-Id: I05df943844c70dc6aa729ab744d2d405cbfe2c76
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/test/mock_ethernet_interface.hpp b/test/mock_ethernet_interface.hpp
index b8c3335..a0358ed 100644
--- a/test/mock_ethernet_interface.hpp
+++ b/test/mock_ethernet_interface.hpp
@@ -13,9 +13,9 @@
 {
   public:
     MockEthernetInterface(sdbusplus::bus_t& bus, const std::string& objPath,
-                          DHCPConf dhcpEnabled, Manager& parent,
-                          bool emitSignal) :
-        EthernetInterface(bus, objPath, dhcpEnabled, parent, emitSignal,
+                          const config::Parser& config, DHCPConf dhcpEnabled,
+                          Manager& parent, bool emitSignal) :
+        EthernetInterface(bus, objPath, config, dhcpEnabled, parent, emitSignal,
                           /*nicEnabled=*/true)
     {
     }