Remove check for %p and %T in printValue.
These verbs are not recursive and are handled already in
printArg which is called on any argument before printValue.

Format the type string for %T directly instead of invoking
the more complex printArg with %s on the type string.

Decouple the %T tests from variables declared in scan_test.go.

Change-Id: Ibd51566bd4cc1a260ce6d052f36382ed05020b48
Reviewed-on: https://go-review.googlesource.com/20622
Run-TryBot: Rob Pike <r@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rob Pike <r@golang.org>