build_matrix: ignore hidden files
build_matrix: ignore hidden files

Signed-off-by: Patrick Donnelly <d35c2028e065409a3eff47e1b4cba347a9379b4b@redhat.com>

SUSE/teuthology,dmick/teuthology,ceph/teuthology,dmick/teuthology,ceph/teuthology,ktdreyer/teuthology,dmick/teuthology,SUSE/teuthology,SUSE/teuthology,ktdreyer/teuthology