fix ls_fallback() to remove 'fallback' option from solver conf
fix ls_fallback() to remove 'fallback' option from solver conf

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