Fix ci build with valgrind (LEVEL=nightmare)

[ololobus]

Now it throws a weird error:

+ valgrind --tool=memcheck --leak-check=no --time-stamp=yes --track-origins=yes --trace-children=yes --gen-suppressions=all --suppressions=/pg/testdir/postgresql/src/tools/valgrind.supp --suppressions=/pg/testdir/valgrind.supp --log-file=/tmp/valgrind-%p.log pg_ctl start -l /tmp/postgres.log -w
438valgrind: /pg/testdir/pg_bin/bin/pg_ctl: Operation not permitted

For example: https://travis-ci.com/github/postgrespro/pg_variables/jobs/418807062#L438

It could be related to a problem with setrlimit(RLIMIT_CORE, &lim); inside container: https://stackoverflow.com/questions/52070477/setrlimit-fails-with-operation-not-permitted-when-run-under-valgrind