Reduce some Error log severities

There are instances of ERROR logs that would work better as WARNING or
DEBUG since they do not actually result in bailing early and returning
an error response.

Signed-off-by: Carson Labrado <clabrado@google.com>
Change-Id: I1e7bca0bb38487b26a4642ab72ce475170bb53c6
diff --git a/redfish-core/lib/update_service.hpp b/redfish-core/lib/update_service.hpp
index af2725a..b538806 100644
--- a/redfish-core/lib/update_service.hpp
+++ b/redfish-core/lib/update_service.hpp
@@ -888,7 +888,7 @@
     }
     else
     {
-        BMCWEB_LOG_ERROR("Unknown software purpose {}", purpose);
+        BMCWEB_LOG_DEBUG("Unknown software purpose {}", purpose);
     }
 }