entry: use map for metadata in ctor

Transition the entry constructor to use the `map<string,string>`
rather than the `vector<string>`.

Tested: UTs pass and daemon still creates logs.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Icf3ead163cc99a1498734d33335fb6da52e6c98c
diff --git a/test/elog_update_ts_test.cpp b/test/elog_update_ts_test.cpp
index cabcb60..fe1089f 100644
--- a/test/elog_update_ts_test.cpp
+++ b/test/elog_update_ts_test.cpp
@@ -61,7 +61,7 @@
     std::string message{"test error"};
     std::string fwLevel{"level42"};
     std::string path{"/tmp/99"};
-    std::vector<std::string> testData{"additional", "data"};
+    std::map<std::string, std::string> testData{{"additional", "data"}};
     phosphor::logging::AssociationList associations{};
 
     Entry elog{bus,
@@ -132,7 +132,7 @@
     std::string message{"test error"};
     std::string fwLevel{"level42"};
     std::string path{"/tmp/99"};
-    std::vector<std::string> testData{"additional", "data"};
+    std::map<std::string, std::string> testData{{"additional", "data"}};
     phosphor::logging::AssociationList associations{};
 
     Entry elog{bus,