crimson/osd: fix no ENOENT when removing already removed object
This patch deals with the following problem:
```
[rzarzynski@o06 build]$ RBD_FEATURES="21" ./bin/ceph_test_cls_rbd --gtest_filter=TestClsRbd.create
Running main() from gmock_main.cc
Note: Google Test filter = TestClsRbd.create
[==========] Running 1 test from 1 test suite.
[----------] Global test environment set-up.
[----------] 1 test from TestClsRbd
[ RUN ] TestClsRbd.create
../src/test/cls_rbd/test_cls_rbd.cc:467: Failure
Expected equality of these values:
-2
ioctx.remove(oid)
Which is: 0
[ FAILED ] TestClsRbd.create (10 ms)
[----------] 1 test from TestClsRbd (10 ms total)
[----------] Global test environment tear-down
[==========] 1 test from 1 test suite ran. (2805 ms total)
[ PASSED ] 0 tests.
[ FAILED ] 1 test, listed below:
[ FAILED ] TestClsRbd.create