Fix duplicate names in test library.

[rpgoldman]

PR Summary

Fix tests with duplicate names. When I tried to run the ert tests, they failed repeatedly, giving errors from tests which had duplicate names. I have tracked these down and replaced them with unique names.

This would be a necessary first step to getting the tests to run again, and generally updating elpy.

PR checklist

Please make sure that the following things have been addressed (and check the relevant checkboxes):

• Commits respect our guidelines
• Tests are passing properly (see here on how to run Elpy's tests)

Tests do not pass properly, but they do not pass on master, either. Failing tests are:

23 unexpected results:
   FAILED  elpy-company-backend-should-add-shell-candidates
   FAILED  elpy-company-backend-should-find-full-prefix-string
   FAILED  elpy-company-backend-should-find-simple-prefix-string
   FAILED  elpy-config--get-config-should-return-keys
   FAILED  elpy-config--get-config-should-set-pythonpath
   FAILED  elpy-eldoc-documentation-should-show-object-onelinedoc
   FAILED  elpy-fold-at-point-should-NOT-fold-and-unfold-functions-from-after
   FAILED  elpy-multiedit-python-symbol-at-point-should-save-some-buffers
   FAILED  elpy-pdb-break-at-point-should-break-at-point
   FAILED  elpy-pdb-debug-buffer-and-break-at-point-should-ignore-breakpoints
   FAILED  elpy-pdb-debug-buffer-from-beginning-should-enter-pdb
   FAILED  elpy-pdb-debug-buffer-should-always-begin-at-first-line
   FAILED  elpy-pdb-debug-buffer-should-continue-with-second-breakpoint
   FAILED  elpy-pdb-debug-buffer-should-enter-pdb
   FAILED  elpy-pdb-debug-buffer-should-forget-previous-breakpoints
   FAILED  elpy-pdb-debug-buffer-should-stop-at-the-first-breakpoint
   FAILED  elpy-pdb-debug-last-exception-should-debug-last-exception
   FAILED  elpy-pdb-debug-last-exception-should-ignore-breakpoints
   FAILED  elpy-pdb-toggle-breakpoint-at-point-should-add-breakpoints
   FAILED  elpy-rpc-get-virtualenv-path-should-return-current-venv-path
   FAILED  elpy-shell-send-file-should-accept-large-strings
   FAILED  elpy-shell-should-echo-outputs
   FAILED  elpy-should-format-code-with-default-formatter

[gopar]

Beautful! Thanks!