Setting the vm_memory_high_watermark to > 1 defaults to total available memory

[gerhard]

free -b
1038778368

Expected:

rabbitmqctl set_vm_memory_high_watermark 0.999999

rabbitmqctl eval 'vm_memory_monitor:get_vm_memory_high_watermark().'
0.99999999

rabbitmqctl eval 'vm_memory_monitor:get_memory_limit().'
1038778357

erl -noshell -eval 'io:format("~p~n", [1038778368 * 0.99999999]).' -eval 'init:stop()'
1038778357.6122162

Unexpected:

rabbitmqctl set_vm_memory_high_watermark 1.0
Setting memory threshold on 'rabbit@rmq0-rmq-swapping' to 1.0

rabbitmqctl eval 'vm_memory_monitor:get_vm_memory_high_watermark().'
1.0

# I expect the memory limit to be set to 1038778368, but instead:
rabbitmqctl eval 'vm_memory_monitor:get_memory_limit().'
415511347

erl -noshell -eval 'io:format("~p~n", [1038778368 * 0.4]).' -eval 'init:stop()'
415511347.20000005

When setting an absolute memory that is higher than the available memory:

set_vm_memory_high_watermark absolute 2000MB
Setting memory threshold on 'rabbit@rmq0-rmq-swapping' to 2000000000 bytes

rabbitmqctl eval 'vm_memory_monitor:get_vm_memory_high_watermark().'
{absolute,2000000000}

rabbitmqctl eval 'vm_memory_monitor:get_memory_limit().'
1038778368