fix Problem.solve() for no active_only
fix Problem.solve() for no active_only

rc/sfepy,vlukes/sfepy,lokik/sfepy,BubuLK/sfepy,rc/sfepy,sfepy/sfepy,BubuLK/sfepy,lokik/sfepy,BubuLK/sfepy,lokik/sfepy,sfepy/sfepy,lokik/sfepy,rc/sfepy,sfepy/sfepy,vlukes/sfepy,vlukes/sfepy