x/blog: test times out on aix-ppc64 builder

[bcmills]

The x/blog test is consistently timing out on the aix-ppc64 builder on release-branch.go1.13 builds (example: https://build.golang.org/log/587d79c987daa7919322215e2230de451ad552f1).

It's not obvious to me whether there is something wrong with the builder (or maybe just slow disk performance?), something wrong with the x/blog test, or some regression in 1.13.

CC @Helflym @trex58 @dmitshur @toothrot @bradfitz

[gopherbot]

Change https://golang.org/cl/192323 mentions this issue: blog: skip test on slow aix-ppc64 builder

[Helflym]

It does work locally, so it should be linked with the builder setup. I don't have time to fix it right now, but I'll try to do it before 1.14.

[laboger]

If I look at the error dump, it shows a stack where it says "stack unavailable". I was told at one time this occurs for code running C (or at least not Go). And then below, the register contents show strange values, it has to be in C code since R0 is not 0 and it has to be 0 for Go. The ctr is a bad value if it is running in a loop that explains why it would time out.

I don't know if there is any way to find out what C code is might be running. I don't know why it would fail in the builder but not in local testing.