lib: Minor static delta fixes

First, the manual crosscheck script bitrotted; it got caught up
in the "use libtest repo creation wrapper" bit, and also it
seems like at some point `pull --require-static-deltas` changed
meaning when dealing with `file:///` repos.  I have more work to
unwind that.

Next, I'm seeing a delta failure which looks like a static delta
miscompilation with rollsums; change the compiler to print out
the source object too, which helped me debug this.

And finally in the processing code, fix incorrect error prefixing, which was
misleading.

Closes: #1311
Approved by: ashcrow

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

@@ -711,7 +711,7 @@ dispatch_write (OstreeRepo                 *repo,
                GCancellable               *cancellable,
                GError                    **error)
 {
-  GLNX_AUTO_PREFIX_ERROR("opcode open-splice-and-close", error);
+  GLNX_AUTO_PREFIX_ERROR("opcode write", error);
   guint64 content_size;
   guint64 content_offset;
 
@@ -816,7 +816,7 @@ dispatch_close (OstreeRepo                 *repo,
                 GCancellable               *cancellable,
                 GError                    **error)
 {
-  GLNX_AUTO_PREFIX_ERROR("opcode open-splice-and-close", error);
+  GLNX_AUTO_PREFIX_ERROR("opcode close", error);
 
   if (state->content_out)
     {