test/osd/TestRados.cc: run test after finishing redirect setup

test/osd/TestRados.cc: run test after finishing redirect setup

set-redirect test creates more objects than default due to redirect mapping
(let's assume that we create 500 objects, oid 1 -> oid 501, oid 2 -> oid 502)
But the test should use objects within pre-defined range. For example,
If the number of object is 500, only 1~500 oid are allowed for test operations.

In the failure cases, test operation tried to use wrong oids (which means
higher than 500). This is because the bug in the setup phase.
If max_inflights > 1, set-redirect can be finished after setup is completed.
(so wrong oid is included in oid_in_use).
We need to completely remove redirect objects in oid_in_use before start the test.

Fixes: http://tracker.ceph.com/issues/20114
Signed-off-by: Myoungwon Oh <omwmw@sk.com>