PEL: Fix some cppcheck warnings

This is the first of two commits to fix most of the cppcheck warnings in
the PEL code.  It doesn't fix all of them because some are false
positives and some are just suggestions.

It's broken up into two commits to make them smaller.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I75937797a6920611b136d600e9efd6c694e4209c
diff --git a/extensions/openpower-pels/json_utils.cpp b/extensions/openpower-pels/json_utils.cpp
index e6007ed..679ef4e 100644
--- a/extensions/openpower-pels/json_utils.cpp
+++ b/extensions/openpower-pels/json_utils.cpp
@@ -167,7 +167,7 @@
 }
 
 void jsonInsert(std::string& jsonStr, const std::string& fieldName,
-                std::string fieldValue, uint8_t indentCount)
+                const std::string& fieldValue, uint8_t indentCount)
 {
     const int8_t spacesToAppend =
         colAlign - (indentCount * indentLevel) - fieldName.length() - 3;
@@ -185,7 +185,8 @@
 }
 
 void jsonInsertArray(std::string& jsonStr, const std::string& fieldName,
-                     std::vector<std::string>& values, uint8_t indentCount)
+                     const std::vector<std::string>& values,
+                     uint8_t indentCount)
 {
     const std::string jsonIndent(indentCount * indentLevel, 0x20);
     if (!values.empty())