ManagedServerBootCmdFactory alters system property values

When ManagedServerBootCmdFactory iterates through system properties to use in the server launch command it adds a value of "true" for any properties that have no value. This is incorrect. In particular it breaks SecurityManager usage as -Djava.security.manager is a valid setting while -Djava.security.manager=true will result in

[Host Controller] 15:09:01,758 INFO [org.jboss.as.host.controller] (Controller Boot Thread) JBAS010922: Starting server server-one
15:10:55,691 INFO [org.jboss.as.process.Server:server-one.status] (ProcessController-threads - 3) JBAS012017: Starting process 'Server:server-one'
[Server:server-one] Error occurred during initialization of VM
[Server:server-one] java.lang.InternalError: Could not create SecurityManager: true
[Server:server-one] at sun.misc.Launcher.<init>(Launcher.java:106)
[Server:server-one] at sun.misc.Launcher.<clinit>(Launcher.java:57)
[Server:server-one] at java.lang.ClassLoader.initSystemClassLoader(ClassLoader.java:1486)
[Server:server-one] at java.lang.ClassLoader.getSystemClassLoader(ClassLoader.java:1468)
[Server:server-one]