XD-206

Consider pre-existing xd.home system property
For both ContainerMain & AdminMain, XD home is set in the following ways:

1) From xd-* scripts, specify "--xdHomeDir" command line option.
   This will override any existing system property "xd.home".
2) If "--xdHomeDir" is not specified, then the "xd.home" system property will
   have the preference
3) If both "--xdHomeDir" and "xd.home" system property are not provided,
   then the relative path ".." is set to be XD home