the token is set when we get the srp token in the keymanager service,
but it wasn't been propagated properly to the internal nicknym object
that was refactored recently.

here I make the setter write the same token to both keymanager itself
and the nicknym.

some little additional refactors:

- move gpg initialization to a helper method
  in this way it becomes easier to stub the soledad and keymanager
  components, for testing.

- name nicknym token as publicly visible, since i'm accessing
  it from the keymanager object.

- Resolves: #8651

- some pep8 problems
- some confusion with old and new code after merging
from old keymanager

Port of the original commit:
8f1fe8dd4a54fd2bdda2fc78c339ce9b3d0fc331
by Zara Gebru that introduced updating keys in the background.

This was made in the legacy leapcode/keymanager repo, but was lost in
the merge to the unified bitmask-dev.

Original commit message follows:
--------------------------------

- refresh random key in random time
- add get key by fingerprint
- refactor nicknym methods to own file
- tests

- note this do not include a check for
revoked key, since that need some changes
in gnupg

- Related: #6089