Update string compares on signal messages

Resulting from a code review, remove the use of strcmp when comparing a
string to a const char*

Change-Id: Idcd3f99bf7ca0151f5f1b97c7ccc54d6e8c56f8e
Signed-off-by: Matthew Barth <msbarth@us.ibm.com>
diff --git a/control/functor.hpp b/control/functor.hpp
index faf0d3e..de04226 100644
--- a/control/functor.hpp
+++ b/control/functor.hpp
@@ -82,10 +82,10 @@
         if (msg)
         {
             std::map<std::string, sdbusplus::message::variant<T>> properties;
-            const char* iface = nullptr;
+            std::string iface;
 
             msg.read(iface);
-            if (!iface || strcmp(iface, _iface))
+            if (iface != _iface)
             {
                 return;
             }
@@ -197,8 +197,7 @@
             sdbusplus::message::object_path op;
 
             msg.read(op);
-            auto objPath = static_cast<const std::string&>(op).c_str();
-            if (!objPath || strcmp(objPath, _path))
+            if (static_cast<const std::string&>(op) != _path)
             {
                 // Object path does not match this handler's path
                 return;