Default to a sane memory limit when container memory is unlimited

[ekcasey]

When running a docker container w/o memory limits the memory calculator currently tries to allocate a LOT of memory, causing the process to hang and then crash.

Example: spring-petclinic

$ docker run <petclinic-image>
Calculated JVM Memory Configuration: -XX:MaxDirectMemorySize=10M -XX:MaxMetaspaceSize=114016K -XX:ReservedCodeCacheSize=240M -Xss1M -Xmx68718850719K (Head Room: 0%, Loaded Class Count: 17716, Thread Count: 250, Total Memory: 70368744177664)
$

With -m 1G the same image runs successfully

$ docker run -m 1G <petclinic-image>
Calculated JVM Memory Configuration: -XX:MaxDirectMemorySize=10M -XX:MaxMetaspaceSize=114016K -XX:ReservedCodeCacheSize=240M -Xss1M -Xmx422559K (Head Room: 0%, Loaded Class Count: 17716, Thread Count: 250, Total Memory: 1073741824)


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 |   |   |   |___  |   | |     |_|       |   | | |   |   |     |_    ) ) ) )
 |___|   |_______| |___| |_______|_______|___|_|  |__|___|_______|  / / / /
 ==================================================================/_/_/_/