librbd,librados,tools: Initialize aio_comp,m_ variables

librbd,librados,tools: Initialize aio_comp,m_ variables

** 1414517 Uninitialized pointer field
CID 1414517 (#1 of 1): Uninitialized pointer field (UNINIT_CTOR)
2. uninit_member: Non-static class member aio_comp is not initialized
in this constructor nor in any functions that it calls.

** 1274324 Uninitialized scalar field
2. uninit_member: Non-static class member m_pool_id is not initialized
in this constructor nor in any functions that it calls.
CID 1274324 (#1 of 1): Uninitialized scalar field (UNINIT_CTOR)
4. uninit_member: Non-static class member m_snap_seq is not initialized
in this constructor nor in any functions that it calls.

** 1356906 Uninitialized scalar field
CID 1356906 (#1-2 of 2): Uninitialized scalar field (UNINIT_CTOR)
5. uninit_member: Non-static class member m_snap_ret is not initialized
in this constructor nor in any functions that it calls.

Signed-off-by: Amit Kumar <amitkuma@redhat.com>