rf: does not refactor definitions inside *pkg*_test files

[magodo]

Got following files:

$ ls
foo_test.go  go.mod  go.sum

$ cat foo_test.go
package foo_test

var X int

$ rf -diff 'mv X Y'
cannot find X
rf: errors found during: mv X Y

There is a similar issue #1 got resolved. The discrepency of this issue is that X is defined in the test package, rather than defined elsewhere.
Additionally, changing the package name from foo_test to foo, then this issue doesn't exist.