xfs: Initialize variables in xfs_alloc_get_rec before using them

Make sure we initialize *bno and *len, before jumping to out_bad_rec
label, and risk calling xfs_warn() with uninitialized variables.

Coverity: 100898
Coverity: 1437081
Coverity: 1437129
Coverity: 1437191
Coverity: 1437201
Coverity: 1437212
Coverity: 1437341
Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>