psusensors: Cleaning up debug and error wording

Rewords some misleading error messages
Adds additional test for failure to set property
Adds additional line for sensor value update
Sensor label head line now shows pairing

Tested: Output appears as expected on my machine

Change-Id: Ibb2ca0df23124120070ca47d4377942089dbbed7
Signed-off-by: Josh Lehan <krellan@google.com>
diff --git a/src/PSUSensor.cpp b/src/PSUSensor.cpp
index e18f739..c5e8e35 100644
--- a/src/PSUSensor.cpp
+++ b/src/PSUSensor.cpp
@@ -118,6 +118,11 @@
             }
             if (static_cast<double>(nvalue) != value)
             {
+                if constexpr (DEBUG)
+                {
+                    std::cerr << "Update " << path << " from " << value
+                              << " to " << nvalue << "\n";
+                }
                 updateValue(nvalue);
             }
             errCount = 0;