oeqa/runlevel : add test for runlevels

This test mimic the boot_from_runlevel_3 and boot_from_runlevel_5 test cases from oeqa/manual/bsp-hw.json.
The boot_from_runlevel_3 and boot_from_runlevel_5 manual test cases should be remove from oeqa/manual/bsp-hw.json if this patch get merged.

Signed-off-by: Teoh Jay Shen <jay.shen.teoh@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>