cmake: prevent ASAN_OPTIONS from detect_odr_violation
turns out we have multiple copies of following symbol defined by rbd executable:
```
AddressSanitizer: odr-violation: global 'ceph::buffer::list::always_empty_bptr' at /home/jenkins-build/build/workspace/ceph-pull-requests/src/common/buffer.cc:1267:34
```
before addressing it. let's disable this warning.