Red Hat Satellite Capsule upgrade fails with error "URL Only one declaration of a proxy is allowed"

Issue

• Red Hat Satellite Capsule upgrade fails with below errors.

  Upgrade Step: Running installer...
  Proxy capsule2.example.com cannot be registered (422 Unprocessable Entity): URL Only one declaration of a proxy is allowed
  /Stage[main]/Foreman_proxy::Register/Foreman_smartproxy[capsule2.example.com]/ensure: change from absent to present failed: Proxy capsule2.example.com cannot be registered (422 Unprocessable Entity): URL Only one declaration of a proxy is allowed
  /Stage[main]/Foreman_proxy::Register/Foreman_smartproxy[capsule2.example.com]: Failed to call refresh: Proxy capsule2.example.com cannot be registered (ApipieBindings::MissingArgumentsError: id): N/A
  /Stage[main]/Foreman_proxy::Register/Foreman_smartproxy[capsule2.example.com]: Proxy capsule2.example.com cannot be registered (ApipieBindings::MissingArgumentsError: id): N/A
  Installing             Done                                               [100%] [......................................................................................]
  Something went wrong! Check the log for ERROR-level output
  The full log is at /var/log/foreman-installer/capsule.log
  Upgrade failed during the installation phase. Fix the error and re-run the upgrade.
  

• Red Hat Capsule server upgrade fails with error Proxy capsule2.example.com cannot be registered (422 Unprocessable Entity): URL Only one declaration of a proxy is allowed