Fixes bug 1087807
A recent refactor of scheduling filters and weights broke the
ignore_hosts and force_hosts functionality. The refactored code would
have only worked if a list of host names (strings) were passed in to
host_manager's get_filtered_hosts(). Unfortunately that's what the unit
tests tested, but the real caller (filter_scheduler) actually passes a
list of HostState class instances.
Unit tests are fixed to pass HostStates and the offending code in the
host_manager has been fixed.
Change-Id: I54a3385da7c095e8ddf26b7536d46a9ee4072a58