cbbackupmgr performance regression - 27% slower on leto

Problem
There looks to be a performance regression in cbbackupmgr, the issue was spotted later because there has been issue with the backup performance cluster leto (CBPS-769)

We know a few months back 6.6 was perform better and was using less resouces. Espically CPU.

Now we notice on older hardware 6.6. performances worst than 6.5.0, but on better hardware it performances better that 6.5.0.

The following results were seens backing up a 100GB bucket from 6.5.0:

CBM 6.5.0: 4m23.556859363s
CBM 6.6.0: 5m34.174214886s

Also the CPU usage has increeased.

In the time period without automated performance testing there has been a number of changes, that could have caused this.

Expectation
For cbbackupmgr 6.6 to preforman equally or better than cbbackupmgr 6.5.