Fix missing lower case in header based auth. (#628)

Signed-off-by: kaizimmerm <kai.zimmermann@bosch-si.com>

hawkbit-security-integration/src/main/java/org/eclipse/hawkbit/security/ControllerPreAuthenticatedSecurityHeaderFilter.java

@@ -132,7 +132,7 @@ public class ControllerPreAuthenticatedSecurityHeaderFilter extends AbstractCont
                 if (LOGGER.isTraceEnabled()) {
                     LOGGER.trace("Found matching ssl issuer hash at position {}", iHeader);
                 }
-                return foundHash;
+                return foundHash.toLowerCase();
             }
             iHeader++;
         }