config_parser: Allow modifying Parser map

This makes it possible to mutate the map owned by the parser. This will
eventually be used for implementing write updates.

Change-Id: I89deb4073a0a3bd59528c6b70fc55b49bc6cd944
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/test/test_ethernet_interface.cpp b/test/test_ethernet_interface.cpp
index e340d7b..ac96190 100644
--- a/test/test_ethernet_interface.cpp
+++ b/test/test_ethernet_interface.cpp
@@ -165,7 +165,7 @@
     fs::path filePath = confDir;
     filePath /= "00-bmc-test0.network";
     config::Parser parser(filePath.string());
-    EXPECT_EQ(servers, parser.getMap().getValueStrings("Network", "DNS"));
+    EXPECT_EQ(servers, parser.map.getValueStrings("Network", "DNS"));
 }
 
 TEST_F(TestEthernetInterface, getDynamicNameServers)
@@ -184,7 +184,7 @@
     fs::path filePath = confDir;
     filePath /= "00-bmc-test0.network";
     config::Parser parser(filePath.string());
-    EXPECT_EQ(servers, parser.getMap().getValueStrings("Network", "NTP"));
+    EXPECT_EQ(servers, parser.map.getValueStrings("Network", "NTP"));
 }
 
 TEST_F(TestEthernetInterface, addGateway)