fix memleak in connect_to_ceph fail

[Ten0]

It appears that the Rados struct not being constructed after rados_create succeeding but before other fallible calls may result in never calling the destructor that should be called after a successful call to rados_create, leading to a memory leak.

This fixes it, by moving the construction of the Rados struct just after the successful rados_create call.

[Xuanwo]

Thank you @Ten0 for this!