[fuel-ci] Ostf gate job is not use snaphots due to too much slaves are attached to this job

[Tatyanka]

Detailed bug description:
https://ci.fuel-infra.org/job/master.fuel-ostf.pkgs.ubuntu.gate_ostf_update/

example of job where snapshot is used :
https://ci.fuel-infra.org/job/master.fuel-ostf.pkgs.ubuntu.gate_ostf_update/186/console
but on last several run it's stopped to work

Steps to reproduce:
 make review in fuel-ostf

Expected results:
 gate test is used snapshot - so deployment step is skipped

Actual result:
 last several runs test executes full deployment cycle

Impact:
Time for feedback increases up to 2.5 h
https://ci.fuel-infra.org/job/master.fuel-ostf.pkgs.ubuntu.gate_ostf_update/

[Bug Checker Bot (bug-checker)]

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[Tatyanka (tatyana-leontovich)]

so looks like latest 6 patches runs on different slaves, bvt how much slaves are under ostf gate? Looks like 3 is mote then enough (we do not have may of review requests there)

[Dmitry Kaigarodеsev (dkaiharodsev)]

the amount of assigned slaves reduced down to 2 slaves per branch