task/install: normalize python3 packages to python36 ones
task/install: normalize python3 packages to python36 ones

EPEL7 has switched over to python3.6 as the main python3. and we started
packaging python bindings for python3.6 since
https://github.com/ceph/ceph-build/pull/1283

Signed-off-by: Kefu Chai <a4b264ee037c625052534d60505bfd0db4776ac4@redhat.com>

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