iotests: fix default machine type detection

iotests: fix default machine type detection

The machine type is being detected based on "-M help" output, and we're
searching for the line ending with " (default)".  However, in downstream
one of the machine types s marked as deprecated might become the
default, in which case this logic breaks as the line would now end with
" (default) (deprecated)".  To fix potential issues here, let's relax
that requirement and detect the mere presence of " (default)" line
instead.

Signed-off-by: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
Message-ID: <20231122121538.32903-1-andrey.drobyshev@virtuozzo.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>