symlinking host config is broken with envs + extra spec constraints

[cyrush]

This logic needs to be updated:

pkg_path =  self.find_spack_pkg_path_from_hash(self.pkg_name, self.spec_hash)

returns, pkg_path:

{'name': 'uberenv-conduit', 'path': '~adios+doc+mpi+openmp+parmetis+python+silo'}