virNWFilterSnoopLeaseFileLoad: Don't typecast 'ipl.timeout'

virNWFilterSnoopLeaseFileLoad: Don't typecast 'ipl.timeout'

Use a temporary variable to avoid memory alignment issues on ARM:

../src/nwfilter/nwfilter_dhcpsnoop.c: In function ‘virNWFilterSnoopLeaseFileLoad’:
../src/nwfilter/nwfilter_dhcpsnoop.c:1745:20: error: cast increases required alignment of target type [-Werror=cast-align]
 1745 |                    (unsigned long long *) &ipl.timeout,
      |

Fixes: 0d278aa089bf3a00bf2d6e56d2f01ea4677190a7
Signed-off-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Martin Kletzander <mkletzan@redhat.com>