PEL: Save registry callout JSON for later

When finding an entry in the PEL message registry, save the callout JSON
section, if there is one, in the returned Entry object.  This also adds
a constructor argument that lets one choose to do this or not, because
it isn't needed when used in peltool.

That JSON will be parsed at a later point.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I757509ced952ce8f07f12c28ab203e5eedf4fd32
diff --git a/extensions/openpower-pels/tools/peltool.cpp b/extensions/openpower-pels/tools/peltool.cpp
index 61fb257..1be5953 100644
--- a/extensions/openpower-pels/tools/peltool.cpp
+++ b/extensions/openpower-pels/tools/peltool.cpp
@@ -40,8 +40,8 @@
 namespace pv = openpower::pels::pel_values;
 
 using PELFunc = std::function<void(const PEL&)>;
-message::Registry registry(getMessageRegistryPath() /
-                           message::registryFileName);
+message::Registry registry(getMessageRegistryPath() / message::registryFileName,
+                           false);
 namespace service
 {
 constexpr auto logging = "xyz.openbmc_project.Logging";