tests/sys/kern/pdwait: adjust test for the addition of CAP_PTRACE

Reviewed by:	markj
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D58586

tests/sys/kern/pdwait.c

@@ -206,7 +206,7 @@ ATF_TC_BODY(enotcap, tc)
 	CAP_ALL(&rights);
 	cap_rights_clear(&rights, CAP_PDWAIT);
 
-	pid = pdfork(&fdp, 0);
+	pid = pdfork(&fdp, PD_PTRACE_CAP);
 	if (pid == 0)
 		_exit(42);
 	ATF_REQUIRE_MSG(pid >= 0, "pdfork failed: %s", strerror(errno));