CloseableByteBuffer currently only uses confined Arena 
for buffer allocation meaning only the thread creating 
the Arena is allowed to access the native memory. When 
using elasticsearch with systemd, our notify-extend 
message is executed on a thread separate from where 
the native memory was allocated. This is causing a 
RuntimeException to be thrown. This changes 
CloseableByteBuffer to allow for a shared Arena as 
well for systemd.