qa/ceph_manager: clean up CephManager.do_rados()

qa/ceph_manager: clean up CephManager.do_rados()

do_rados() prefixes extra arguments to every command because they are
helpful during execution of tests with teuthology. This patch
eliminates these extra arguments entirely (through overriding) for test
executions with vstart_runner.py.

Note: "timeout 120" is now prefixed to rados commands too. AFAIS, it
shouldn't have any side-effects on anything.

This commit is similar to commit 93677576c1fd6d0e4e2991a9ba6be6d222ea98ea.

Signed-off-by: Rishabh Dave <ridave@redhat.com>