hostapd_cli: Fix segmentation fault with interface command
ctrl_ifname was not being freed and allocated consistently by using
proper functions: os_free() and os_strdup(). This can result in
segmentation fault when these OS specific wrappers use different
implementation (e.g., with CONFIG_WPA_TRACE=y).
Signed-off-by: Eduardo Abinader <eduardo.abinader@openbossa.org>