debian/control: update yaml-cpp version if building with Jaeger
jaeger specifically requires yaml-dev +0.6 but since all supported
distro(bionic) still doesn't have this version, yaml-cpp will be build
from source if enabled.
This fixes the build failure:
```
Could NOT find yaml-cpp: Found unsuitable version "", but required is at
least "0.5.1" (found yaml-cpp_LIBRARY-NOTFOUND)
```
projects / ceph.git / commit