Use kwalletd5 in KDE 5 environments

KWallet in KDE 5 has updated DBus and desktop names. By default the detected
desktop environment is used to configure KWallet. Alternatively, passing
kwallet5 or kwallet to --password-store will respectively set kwalletd5 or
kwalletd.

* Pass the desktop environment as a parameter to unit tests. Note that
  GetAllLoginsErrorHandling is unchanged, but grouped with the rest of
  NativeBackendKWalletTest cases.
* Error messages use kwalletd or kwalletd5.

BUG=500281

Review URL: https://codereview.chromium.org/1383303002

Cr-Commit-Position: refs/heads/master@{#352620}
4 files changed