Rename ostree-cmdprivate to drop out of introspection

I was looking at our `.gir` and noticed we had the cmdprivate bits
because the pattern for excluding headers is `-private.h`, which
didn't match `cmdprivate.h`.

src/libostree/ostree-cmd-private.c

@@ -19,7 +19,7 @@
 
 #include "config.h"
 
-#include "ostree-cmdprivate.h"
+#include "ostree-cmd-private.h"
 #include "ostree-repo-private.h"
 #include "ostree-core-private.h"
 #include "ostree-repo-static-delta-private.h"

src/libostree/ostree-impl-system-generator.c

@@ -32,7 +32,7 @@
 
 #include "ostree.h"
 #include "ostree-core-private.h"
-#include "ostree-cmdprivate.h"
+#include "ostree-cmd-private.h"
 
 #ifdef HAVE_LIBMOUNT
 typedef FILE OtLibMountFile;

src/libostree/ostree-repo-static-delta-core.c

@@ -25,7 +25,7 @@
 #include "ostree-core-private.h"
 #include "ostree-repo-private.h"
 #include "ostree-lzma-decompressor.h"
-#include "ostree-cmdprivate.h"
+#include "ostree-cmd-private.h"
 #include "ostree-checksum-input-stream.h"
 #include "ostree-repo-static-delta-private.h"
 #include "otutil.h"