Do not fail the /thread/thread4 test if prlimit() fails
Do not fail the /thread/thread4 test if prlimit() fails

This happens on the Debian buildds.

[smcv: Use g_test_skip()]

Forwarded: no, Debian buildd specific

endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib,endlessm/glib