elpa: prefer 2016.05.004 until sse/avx/avx2 issues are resolved (#13530)

- configuration fails on newer versions when enabling sse/avx/avx2
- prefer an older version that will build with these features

var/spack/repos/builtin/packages/elpa/package.py

@@ -21,7 +21,7 @@ class Elpa(AutotoolsPackage):
     version('2017.05.003', sha256='bccd49ce35a323bd734b17642aed8f2588fea4cc78ee8133d88554753bc3bf1b')
     version('2017.05.002', sha256='568b71024c094d667b5cbb23045ad197ed5434071152ac608dae490ace5eb0aa')
     version('2016.11.001.pre', sha256='69b67f0f6faaa2b3b5fd848127b632be32771636d2ad04583c5269d550956f92')
-    version('2016.05.004', sha256='08c59dc9da458bab856f489d779152e5506e04f0d4b8d6dcf114ca5fbbe46c58')
+    version('2016.05.004', sha256='08c59dc9da458bab856f489d779152e5506e04f0d4b8d6dcf114ca5fbbe46c58', preferred=True)
     version('2016.05.003', sha256='c8da50c987351514e61491e14390cdea4bdbf5b09045261991876ed5b433fca4')
     version('2015.11.001', sha256='c0761a92a31c08a4009c9688c85fc3fc8fde9b6ce05e514c3e1587cf045e9eba')