pypy: fix failing test files with Pypy5.6.0

Pypy 5.6.0 saves cached bytecode files in __pycache__ directory, clean them in
tests to fix loading old test extensions code.

Doing so should also helps for Python3.x migration.

tests/test-commandserver.t

@@ -234,7 +234,9 @@ check that local configs for the cached repo aren't inherited when -R is used:
   *** runcommand --config hooks.pre-identify=python:hook.hook id
   eff892de26ec tip
 
+Clean hook cached version
   $ rm hook.py*
+  $ rm -Rf __pycache__
 
   $ echo a >> a
   >>> import os

tests/test-fncache.t

@@ -270,7 +270,11 @@ Aborting transaction prevents fncache change
   > cmdtable = {}
   > 
   > EOF
+
+Clean cached version
   $ rm -f "${extpath}c"
+  $ rm -Rf "`dirname $extpath`/__pycache__"
+
   $ touch z
   $ hg ci -qAm z
   transaction abort!
@@ -305,7 +309,11 @@ Aborted transactions can be recovered later
   > cmdtable = {}
   > 
   > EOF
+
+Clean cached versions
   $ rm -f "${extpath}c"
+  $ rm -Rf "`dirname $extpath`/__pycache__"
+
   $ hg up -q 1
   $ touch z
   $ hg ci -qAm z 2>/dev/null