pldmd: make invalid cmdline arguments cause exit

These invalid invocations will print the usage message but the program
will run anyway:
  pldmd -v 2
  pldmd -z

Running pldmd with no arguments is supported and valid but the usage
message is shown.

The expected behavior when an application is invoked with invalid
arguments is that the program will exit.  The expected behavior when an
application is invoked with valid arguments is that it will not print
any error messages.  Fix the argument parsing code so it matches
expectations.

Change-Id: Iaa38fd0bfb1d1597ff44996f88e8cc0081df306a
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/pldmd/pldmd.cpp b/pldmd/pldmd.cpp
index 38ee7cd..f009e88 100644
--- a/pldmd/pldmd.cpp
+++ b/pldmd/pldmd.cpp
@@ -147,12 +147,13 @@
                     break;
                 default:
                     optionUsage();
-                    break;
+                    exit(EXIT_FAILURE);
             }
             break;
-        default:
-            optionUsage();
+        case -1:
             break;
+        default:
+            exit(EXIT_FAILURE);
     }
 
     /* Create local socket. */