build-appliance-image: fix lost net connectivity after restart

build-appliance-image: fix lost net connectivity after restart

The issue is that an ethernet config file is removed without
proper checks in place (rm -f), which triggers an error and
makes the connman startup script to fail.

The file is now removed with proper checks in place.

Fixes [YOCTO #4003].

(From OE-Core rev: d9349e6e28cef107ad8bd00767ceba4d8aa464dd)

Signed-off-by: Cristian Iorga <cristian.iorga@intel.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>