Update test_series.py

Change test to ensure s.reshape(s.shape) equals a.
Fix GH 4554

order can't be a positional argument to ndarray.reshape
TST assert Series.reshape works as expected

See #4554 and #4659 for a discussion about the expected behavoir.
TST Fix Series.reshape() test.
FIX #4554 and other issues with Series.reshape()

The intended behavoir is: s.reshape() returns the same as s.values.reshape()
except that it returns s itself if the shape does not change.
DOC add fix for #4626 to release notes