kola/tests: Add valid SUID binaries in /usr/bin

The mount.nfs and unix_chkpwd binaries used to reside in sbin, but
after switching to the merged-usr filesystem layout, sbin became a
symlink to bin. But keep the entries for sbin too, for older Flatcar
versions.

kola/tests/misc/files.go

@@ -115,14 +115,16 @@ func SUIDFiles(c cluster.TestCluster) {
 		"/usr/bin/man",
 		"/usr/bin/mandb",
 		"/usr/bin/mount",
+		"/usr/bin/mount.nfs",
 		"/usr/bin/newgidmap",
 		"/usr/bin/newgrp",
 		"/usr/bin/newuidmap",
 		"/usr/bin/passwd",
 		"/usr/bin/pkexec",
-		"/usr/bin/umount",
 		"/usr/bin/su",
 		"/usr/bin/sudo",
+		"/usr/bin/umount",
+		"/usr/bin/unix_chkpwd",
 		"/usr/lib/polkit-1/polkit-agent-helper-1",
 		"/usr/lib64/polkit-1/polkit-agent-helper-1",
 		"/usr/libexec/dbus-daemon-launch-helper",