Enable providing username/password for read operations
Enable providing username/password for read operations

Currently notary fails to authenticate private Docker repositories.
That is, notary fetch a token from `auth.docker.io` but receives 401
(since basic authentication is required to fetch the bearer token for
private Docker repositories).

Since the `AuthenticationHandler` succeed, we must retry the entire flow
with a different handler.

Signed-off-by: Liron Levin <8a32d27d9714af2471a1e7de2e0fcfa9b41f7c72@twistlock.com>

rillig/docker.github.io,BSWANG/denverdino.github.io,sanscontext/docker.github.io,vdemeester/notary,docker/docker.github.io,danix800/docker.github.io,aduermael/docker.github.io,HuKeping/notary,LuisBosquez/docker.github.io,shubheksha/docker.github.io,vdemeester/notary,aduermael/docker.github.io,docker/docker.github.io,menglingwei/denverdino.github.io,troy0820/docker.github.io,troy0820/docker.github.io,cyli/notary,shubheksha/docker.github.io,jfrazelle/notary,phiroict/docker,JimGalasyn/docker.github.io,gdevillele/docker.github.io,johnsandiford/notary,shin-/docker.github.io,docker-zh/docker.github.io,BSWANG/denverdino.github.io,joaofnfernandes/docker.github.io,londoncalling/docker.github.io,denverdino/denverdino.github.io,thaJeztah/docker.github.io,danix800/docker.github.io,bdwill/docker.github.io,johnstep/docker.github.io,jzwlqx/denverdino.github.io,shin-/docker.github.io,docker/notary,docker/docker.github.io,shin-/docker.github.io,sanscontext/docker.github.io,bdwill/docker.github.io,menglingwei/denverdino.github.io,shin-/docker.github.io,londoncalling/docker.github.io,jfrazelle/notary,joeuo/docker.github.io,LuisBosquez/docker.github.io,denverdino/denverdino.github.io,alexisbellido/docker.github.io,troy0820/docker.github.io,denverdino/docker.github.io,jzwlqx/denverdino.github.io,endophage/notary,umayr/notary,denverdino/docker.github.io,shubheksha/docker.github.io,anweiss/docker.github.io,umayr/notary,jzwlqx/denverdino.github.io,alexisbellido/docker.github.io,johnstep/docker.github.io,thaJeztah/docker.github.io,sanscontext/docker.github.io,jfrazelle/notary,JimGalasyn/docker.github.io,dqminh/notary,aduermael/docker.github.io,BSWANG/denverdino.github.io,denverdino/denverdino.github.io,andrewhsu/notary,joaofnfernandes/docker.github.io,johnstep/docker.github.io,menglingwei/denverdino.github.io,johnstep/docker.github.io,menglingwei/denverdino.github.io,londoncalling/docker.github.io,denverdino/docker.github.io,londoncalling/docker.github.io,jzwlqx/denverdino.github.io,joeuo/docker.github.io,phiroict/docker,bdwill/docker.github.io,joeuo/docker.github.io,umayr/notary,anweiss/docker.github.io,denverdino/denverdino.github.io,gdevillele/docker.github.io,LuisBosquez/docker.github.io,gdevillele/docker.github.io,denverdino/docker.github.io,joeuo/docker.github.io,alexisbellido/docker.github.io,JimGalasyn/docker.github.io,thaJeztah/docker.github.io,LuisBosquez/docker.github.io,docker/notary,johnstep/docker.github.io,vdemeester/notary,joeuo/docker.github.io,cyli/notary,phiroict/docker,anweiss/docker.github.io,joaofnfernandes/docker.github.io,JimGalasyn/docker.github.io,shin-/docker.github.io,joaofnfernandes/docker.github.io,gdevillele/docker.github.io,bdwill/docker.github.io,johnsandiford/notary,HuKeping/notary,danix800/docker.github.io,docker-zh/docker.github.io,sanscontext/docker.github.io,anweiss/docker.github.io,endophage/notary,thaJeztah/docker.github.io,dqminh/notary,andrewhsu/notary,danix800/docker.github.io,JimGalasyn/docker.github.io,docker/notary,rillig/docker.github.io,BSWANG/denverdino.github.io,rillig/docker.github.io,joaofnfernandes/docker.github.io,denverdino/docker.github.io,troy0820/docker.github.io,denverdino/denverdino.github.io,docker-zh/docker.github.io,shubheksha/docker.github.io,docker-zh/docker.github.io,BSWANG/denverdino.github.io,bdwill/docker.github.io,phiroict/docker,anweiss/docker.github.io,jzwlqx/denverdino.github.io,sanscontext/docker.github.io,endophage/notary,phiroict/docker,aduermael/docker.github.io,andrewhsu/notary,menglingwei/denverdino.github.io,rillig/docker.github.io,docker/docker.github.io,LuisBosquez/docker.github.io,johnsandiford/notary,docker-zh/docker.github.io,thaJeztah/docker.github.io,dqminh/notary,shubheksha/docker.github.io,docker/docker.github.io,gdevillele/docker.github.io,londoncalling/docker.github.io,cyli/notary,HuKeping/notary,alexisbellido/docker.github.io,alexisbellido/docker.github.io