systemctl: fix typo in help text
machinectl: fix warning when compiling with -Og

src/machine/machinectl.c: In function ‘openpt_in_namespace’:
src/machine/machinectl.c:623:44: warning: ‘master’ may be used uninitialized in this function [-Wmaybe-uninitialized]
                         close_nointr_nofail(master);
                                            ^