Exec1: batsim_command prewrite may prevent relaunchability

[mpoquet]

When running execN with the -p option, the variables.bash is overwritten.

However, since batsim_command.bash contains the actual previous values of variables instead of pointers, the batsim_command.bash and sched_command.bash may contain different variable values (i.e. socket port).

Fix proposal: instead of prewriting batsim_command.bash, prewrite another temporary file instead and write batsim_command.bash without actual variable values.

[mpoquet]

Fixed in 3c14d01. The prewriting was already done in a temporary file, but the in-memory batsim_command was overwritten by mistake.