busybox: remove coreutils dependency in busybox-ptest

busybox: remove coreutils dependency in busybox-ptest

A dependency on coreutils was added to busybox-ptest in oe-core 658c5ed
to fix a test failure.

The failure is because one of the start-stop-daemon tests is known to
fail if /bin/false is busybox. Instead of failing, we can check if
/bin/false is a symlink to busybox and skip the test if so.

[ YOCTO #15068 ]

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>