Upgrade helper script in small tests to python3

[NelsonVides]

Heh, there was some old usage of python2 in the small tests that was forgotten 😄

[mongoose-im]

8782.1 / Erlang 23.0.3 / small_tests / 5e4f1ce
Reports root / small

---

8782.2 / Erlang 23.0.3 / internal_mnesia / 5e4f1ce
Reports root/ big
OK: 1495 / Failed: 0 / User-skipped: 168 / Auto-skipped: 0

---

8782.3 / Erlang 23.0.3 / odbc_mssql_mnesia / 5e4f1ce
Reports root/ big
OK: 2771 / Failed: 0 / User-skipped: 228 / Auto-skipped: 0

---

8782.4 / Erlang 23.0.3 / mysql_redis / 5e4f1ce
Reports root/ big
OK: 2766 / Failed: 0 / User-skipped: 233 / Auto-skipped: 0

---

8782.5 / Erlang 23.0.3 / riak_mnesia / 5e4f1ce
Reports root/ big
OK: 1629 / Failed: 0 / User-skipped: 180 / Auto-skipped: 0

---

8782.6 / Erlang 23.0.3 / ldap_mnesia / 5e4f1ce
Reports root/ big
OK: 1405 / Failed: 0 / User-skipped: 258 / Auto-skipped: 0

[arcusfelis]

ok

[chrzaszcz]

Looks good, but @arcusfelis do not merge code that is pending review.