fix ProblemDefinition.solve() for LCBCs
fix ProblemDefinition.solve() for LCBCs

- revert setting of current time step data

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