text: Title: [PR] Fix an issue with mistakenly added Bearer auth in addition to Basic auth
  Body: > <a href="https://github.com/nolar"><img align="left" height="50" src="https://avatars0.githubusercontent.com/u/544296?v=4"></a>        A pull request by [nolar](https://github.com/nolar) at _2019-11-19 22:31:04+00:00_
  > Original URL: https://github.com/zalando-incubator/kopf/pull/243
  > Merged by [nolar](https://github.com/nolar) at _2019-11-19 23:55:13+00:00_
  
  > Issue : #242
  
  ## Description
  
  `Authorization: Bearer` header was sent (without a token!) because there was a schema defined by default (`"Bearer"`), which should not be there (`None`).
  
  This caused problems when Basic auth (username+password) was used — it could not co-exist with `Authorization: Bearer` header.
  
  ## Types of Changes
  
  - Bug fix (non-breaking change which fixes an issue)
  
  
  ---
  
  > <a href="https://github.com/dneuhaeuser-zalando"><img align="left" height="30" src="https://avatars2.githubusercontent.com/u/37899626?v=4"></a>            Commented by [dneuhaeuser-zalando](https://github.com/dneuhaeuser-zalando) at _2019-11-19 23:12:50+00:00_
  > &nbsp;
  
  Approved because I understand it's somewhat urgent but ideally this should have a test, to ensure this fixes the problem and to prevent a regression.
  
  ---
  
  > <a href="https://github.com/nolar"><img align="left" height="30" src="https://avatars0.githubusercontent.com/u/544296?v=4"></a>            Commented by [nolar](https://github.com/nolar) at _2019-11-20 01:01:26+00:00_
  > &nbsp;
  
  The tests for this case are added post-factum in #244 (with other auth/ssl tests).