Disabling nightly test of FiniteElasticity/Membrane/MembraneExtension2DSpace example

The test will be re-enabled when the discrepancy between example output and expected output has been investigated and corrected.

Tracker Item 2428
Merge pull request #69 from PrasadBabarendaGamage/master

Disabling nightly test of FiniteElasticity MembraneExtension2DSpace example