include,messages,rbd: Initialize counter,group_pool

include,messages,rbd: Initialize counter,group_pool

Fixes the coverity issues:

** 1396182 Uninitialized scalar field
CID 1396182 (#1 of 1): Uninitialized scalar field (UNINIT_CTOR)
2. uninit_member: Non-static class member counter is not initialized
in this constructor nor in any functions that it calls.

** 1396194 Uninitialized scalar field
CID 1396194 (#1 of 1): Uninitialized scalar field (UNINIT_CTOR)
2. uninit_member: Non-static class member group_pool is not initialized
in this constructor nor in any functions that it calls

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