update linear_elastic_mM.py example to regenerate coefficients
update linear_elastic_mM.py example to regenerate coefficients

- fixes race condition with several travis runs

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