skip SLP discovery if SMT is used, use the URL from config file (bnc#886423)
allow changing the registration server when re-registering
reset registration status when upgrade fails (bnc#886387)

to allow re-registering from scratch
move "reset_registration_status" method from client to lib
- 3.1.90
properly return upgrade result value
Merge pull request #132 from yast/workflow_fixes

Workflow fixes