activation group should not overwrite system properties

In the current implementation, the activation group overwrites the set
of system properties defined when the child process creates the group.
The system properties (e.g., java.home, os.version, etc.) should not
be overwritten. Instead, when an ActivationGroupDesc is created, it
should remove properties that are system specific. The only properties
that are not system specific, in the following list, are the user.*
properties. The other properties should be removed from the list of
properties given to the ActivationGroupDesc constructor. Also, in
the ActivationGroupImpl constructor, the system properties should not
be overridden; each property specified in the ActivationGroupDesc's
MarshalledObject should be added, one by one, to the current set
of properties for the VM.

- listing properties --
java.specification.name=Java Platform API Specification
java.version=jackson:12.05.97-03:10
java.awt.graphicsenv=sun.awt.X11GraphicsEnvironment
java.tmpdir=/var/tmp/
user.timezone=EST
java.specification.version=jackson:12.05.97-03:10
user.home=/home/ann
java-vm.name=non-JIT
os.arch=sparc
java.awt.fonts=/usr/openwin/lib/X11/fonts/Type1
java.vendor.url=http://www.sun.com/
file.encoding.pkg=sun.io
java-vm.specification.vendor=Sun Microsystems Inc.
java.home=/js/files/JDK1.2/build/solaris/bin/..
java-vm.specification.version=1.0
java.class.path=.:/js/files/JDK1.2/build/solaris/clas...
line.separator=

os.name=SunOS
java.vendor=Sun Microsystems Inc.
java.library.path=/js/files/JDK1.2/build/solaris/bin/.....
java-vm.version=jackson:12.05.97-03:10
file.encoding=8859_1
java.specification.vendor=Sun Microsystems Inc.
user.language=en
user.name=ann
java.vendor.url.bug=http://java.sun.com/cgi-bin/bugreport...
java.class.version=45.3
os.version=5.5.1
path.separator=:
java-vm.specification.name=Java Virtual Machine Specification
file.separator=/
user.dir=/home/ann/rmi/bugs/activation
java-vm.vendor=Sun Microsystems Inc.