runqemu: add ability to skip using an existing tap device

runqemu: add ability to skip using an existing tap device

Support the sitauation where a user could have another VM running
which uses tap devices. To prevent runqemu from trying to use the
same tap device, runqemu will skip using a tap device if it finds
a filename tapX.skip within its lock directory.

This fixes [YOCTO #5815]

(From OE-Core rev: 2e490f3b08176b20fe41c64cf17ecf3b5af61f39)

Signed-off-by: Scott Garman <scott.a.garman@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>