[uss_qualifier] Fix aggregate queries stats for #343

[Shastick]

Initial investigation into, and subsequent fix for #343.

This also:

• adds a simple unit test to confirm that the basic thing is working as expected (although the issue was unrelated to the method being tested).
• adds an additional record_note with the exact times that were used to compute the statistic (with the hope that it might help troubleshoot any future bugs and give more information to USS's that fail this check)

Before the fix we would have duplicate times being considered in the statistics computation:

Computed durations: 
init=
[0.009221, 0.017303, 0.006969, 0.015645, 0.019991, 0.020171, 0.019669, 0.022012, 0.024948, 0.024175, 0.023265, 0.022342, 0.02261, 0.026369, 0.02529, 0.024384, 0.024189, 0.024016, 0.022973, 0.020148, 0.016649, 0.010734, 0.007285, 0.010437, 0.007551]
subsequent=
[0.009221, 0.017303, 0.006969, 0.015645, 0.019991, 0.020171, 0.019669, 0.022012, 0.024948, 0.024175, 0.023265, 0.022342, 0.024381, 0.024381, 0.02261, 0.026369, 0.024578, 0.024578, 0.02336, 0.02336, 0.022722, 0.022722, 0.02529, 0.019169, 0.019169, 0.021319, 0.021319, 0.024384, 0.024189, 0.023463, 0.023463, 0.020018, 0.020018, 0.024016, 0.02004, 0.02004, 0.019751, 0.019751, 0.020949, 0.020949, 0.022973, 0.019569, 0.019569, 0.021984, 0.021984, 0.020148, 0.016649, 0.010734, 0.007285, 0.010437, 0.007551]

After the fix, we now have:

 Note: uss3/display_data details -> 
 Initial durations: 
 [0.01803, 0.02747, 0.006678, 0.015086, 0.020754, 0.017331, 0.022996, 0.019715, 0.024693, 0.023738, 0.024164, 0.037216, 0.023981, 0.024089, 0.024049, 0.024908, 0.025497, 0.025069, 0.025, 0.051053, 0.024023, 0.023673, 0.018797, 0.017193, 0.021442, 0.007035, 0.011693, 0.006912] 
 subsequent durations: 
 [0.033204, 0.025565, 0.03087, 0.02483, 0.021935, 0.021839, 0.023704, 0.025428, 0.018601, 0.019487]

These are clearly different.