daemon: fix add_lockspace that has been removed
    
    If rem_lockspace happens
    - after the lease_thread from add_lockspace has
      acquired the lease, and
    - before the space struct is moved to spaces list
    
    then the struct space is freed, which leaves the
    lease_thread using a freed struct space.  The next
    time the lease_thread tries to renew, it will
    probably complain about bad info in struct space
    and/or segfault.
    
    rem_lockspace also needs to check for the lockspace
    on the spaces_add list, otherwise it will return
    immediately, before the remove, if the lockspace
    is being added.
    
    Signed-off-by: David Teigland <teigland@redhat.com>