tests: bulk changes to avoid whitespace errors of check-code.py

This is a part of preparation to apply checking with check-code.py on
code fragments embedded in *.t test scripts.

This revision avoids "whitespace" errors of check-code.py below:

  - missing whitespace after ","
  - missing whitespace in expression
  - no whitespace around "=" for named parameters
  - wrong whitespace around "="

tests/test-bundle2-pushback.t

@@ -25,7 +25,8 b''
   >                   b'key': b'new-server-mark',
   >                   b'old': b'',
   >                   b'new': b'tip'}
-  >         encodedparams = [(k, pushkey.encode(v)) for (k,v) in params.items()]
+  >         encodedparams = [(k, pushkey.encode(v))
+  >                           for (k, v) in params.items()]
   >         op.reply.newpart(b'pushkey', mandatoryparams=encodedparams)
   >     else:
   >         op.reply.newpart(b'output', data=b'pushback not enabled')