task tic can be after toc

During re-partitioning we occasionally see:

[0001] [00015.9] partition.c:repart_edge_metis():463: Bad task weight (-2147483648).

Checking the values of tic and toc shows that these can time reversed, for instance I can see:

t->toc = 487903733871255
t->tic = 487903781581590

This is easily reproduced by forcing a large number of re-partitions and running a SodShock test like:

mpirun -np 2 ../swift_mpi -s -t 6 -v 1 sodShock.yml

Current master at: 6d9f54ae, using modules swift/c4/intel/intelmpi/5.1.2 on cosma-e. Configured using ./configure --with-metis.