Increased the maximum number of open file descriptors on macOS.

Travis-ci: needed the "ulimit -n <value>" call, because found
that the tests fail without it even with launchctl limit tool set.

Gitlab-ci: needed the "launchctl limit maxfiles <value>" call,
because under gitlib-ci it is needed the password to change the
limits and we call the sudo tool which separates the local set
of the environment.

Closes #4373