Update to print error if error on startup

[blainemotsinger]

msm should print any error on startup to help with diagnosing issues.

previously reported issue here:

More details: I modified the main msm script to print out the invocation it was using, then ran that manually. I got this:

$ java -Xms1024M -Xmx1024M -jar /mnt/minecraft/msm/servers/Bean/server.jar nogui
Error: LinkageError occurred while loading main class net.minecraft.server.Main
	java.lang.UnsupportedClassVersionError: net/minecraft/server/Main has been compiled by a more recent version of the Java Runtime (class file version 60.0), this version of the Java Runtime only recognizes class file versions up to 55.0

Searching the error on the webs, I found this Reddit post. Running the following upgraded my JDK and fixed it for me:

$ sudo apt install openjdk-17-jdk

I'm sure I should have known about the increased Java version requirement (bad system admin), but glad it's all working now!

Originally posted by @tomscallon in #390 (comment)