extension: use map in create extension

Adjust the Create extension to use a map for metadata instead of
vector.

Tested: Unit tests updated and passing.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I9bd62b8dcc8b18a61958ed64de98b52a48333637
diff --git a/extensions/openpower-pels/additional_data.hpp b/extensions/openpower-pels/additional_data.hpp
index 09dbd20..74abce9 100644
--- a/extensions/openpower-pels/additional_data.hpp
+++ b/extensions/openpower-pels/additional_data.hpp
@@ -38,19 +38,9 @@
      * @param[in] ad - the AdditionalData property vector with
      *                 entries of "KEY=VALUE"
      */
-    explicit AdditionalData(const std::vector<std::string>& ad)
-    {
-        for (auto& item : ad)
-        {
-            auto pos = item.find_first_of('=');
-            if (pos == std::string::npos || pos == 0)
-            {
-                continue;
-            }
-
-            _data[item.substr(0, pos)] = std::move(item.substr(pos + 1));
-        }
-    }
+    explicit AdditionalData(const std::map<std::string, std::string>& ad) :
+        _data(ad)
+    {}
 
     /**
      * @brief Returns the value of the AdditionalData item for the