fix(unittests): stub BaseNode.wait_ssh_up() in tests
fix(unittests): stub BaseNode.wait_ssh_up() in tests

since #2079 was merged, a call to wait_ssh_up was cause unittest to timeout
on a few tests that inherit from BaseNode

scylladb/scylla-longevity-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-longevity-tests,scylladb/scylla-cluster-tests,scylladb/scylla-longevity-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests