oeqa/targetcontrol: Rework exception handling to avoid warnings
We're seeing:
WARNING: bitbake/lib/bb/cookerdata.py:136: ResourceWarning: unclosed file <_io.FileIO
name='tmp/work/qemux86_64-poky-linux/core-image-minimal/1.0-r0/testimage/qemurunner_log.
20200601181912'
mode='ab' closefd=True
which can only be caused by the qemu.stop() method not being called.
Tweak the error handling to fix the blanket exception handler which
is likely meaning this function isn't getting called.
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
