Fix cosbench-librados build errors/warnings

 .. classpath entries (cosbench-* refs) were missing
 .. test/ directory was missing from build props

Signed-off-by: Tushar Gohad <tushar.gohad@intel.com>
Fix pack.sh permissions

Signed-off-by: Tushar Gohad <tushar.gohad@intel.com>
Add per-stage timestamping, minor stage naming fixes

... useful for post-processing COSbench logs

Signed-off-by: Tushar Gohad <tushar.gohad@intel.com>
Perform authentication once and cache token

COSbench currently uses as many authentication threads
as number of workers at each stage.  Each authentication
thread performs identical operation and in return receives
the same authentication token.  In most case, this is
redundant -- one authentication worker is enough to obtain
auth token and remaining workers can reuse the same.

Signed-off-by: Tushar Gohad <tushar.gohad@intel.com>