Always list a "all" and "clean" targets and remove the similar code
in the tealeaf reader.

This fixes the clean-step falling back to "all" in server-mode.

Task-number: QTCREATORBUG-17138
Change-Id: I1ce84f03c2e9829e4bb5f550c10cdef772fabf5b
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>