Create server and set jargroup do not create jar symlinks

[jives]

Problem

Commands using server_set_jar() like msm server create <server-name> or msm <server-name> jar minecraft
throw an su error (user does not exist) and will not generate symlinks to the latest jar-file in the jargroup(s).

Cause

Wrong variable name used in https://github.com/marcuswhybrow/minecraft-server-manager/blob/master/init/msm#L1019; used ${SERVER_USER[$1]} but should be ${SERVER_USER_NAME[$1]}, therefore su gets passed a blank username if the defaults from msm.conf are used.

Fix

Change ${SERVER_USER[$1]} to ${SERVER_USER_NAME[$1]} in line 1019 of /init/msm