Linux系统中切换DHCP和STATIC模式出现长时间不能连上wifi的问题，
分析log发现是wpa_supplicant问题，mark之
problem
1511502263.447980: rfkill: Cannot open RFKILL control device
1511502263.538880: ctrl_iface exists and seems to be in use - cannot override it
1511502263.539083: Delete '/var/run/wpa_supplicant/ra0' manually if it is not used anymore
1511502263.539316: Failed to initialize control interface '/var/run/wpa_supplicant'.
You may have another wpa_supplicant process already running or the file was
left by an unclean termination of wpa_supplicant in which case you will need
to manually remove this file before starting wpa_supplicant again.##
不使用 systemd
直接删除可以解决问题？