user priority test showed unexpected performance behavior

Build tested: 1.2.3-1 from buildbot

server commit:
61f32f2
engine commit:
46cc344

The mixed user test showed the following performance timing:
Mixed user types
----------------
HighUser = 9.080 sec @ priority 100
MediumUser = 9.352 sec @ priority 66
LowUser = 7.283 sec @ priority 33
NoPriUser = 3.402 sec @ priority 33

Few days ago, the same test return the following expected result:

Mixed user types
----------------
HighUser = 4.106 sec @ priority 100
MediumUser = 5.757 sec @ priority 66
LowUser = 9.107 sec @ priority 33
NoPriUser = 9.258 sec @ priority 33