poky-qemu-internal: implement file locking in bash
There does not appear to be a universal lockfile utility that
meets our needs. For example:
* 'lockfile' is part of the procmail pacakge in Ubuntu, a
requirement we don't want to impose on our users
* lockfile-[create|remove] from the Ubuntu lockfile-progs
package does not appear to be available in Fedora/openSUSE
So, the most portable way to do this is just to implement it
in bash. The likelihood of race conditions is minimal for
what we need this for.
Signed-off-by: Scott Garman <scott.a.garman@intel.com>
