PP-741: Need a default job specific to Cray in PTL

Target Release	17.2.1
JIRA	PP-741 - Getting issue details... STATUS
Document status	Initial version
Document owner	Sanket Borle (Deactivated)
Designer	Sanket Borle (Deactivated)
Developers	Sanket Borle (Deactivated)
QA	Kumar Jakkali (Deactivated) sarita kh (Deactivated)
Forum Discussion	http://community.pbspro.org/t/pp-741-need-a-default-job-specific-to-cray-in-ptl/500

Interface:Job()
Visibility: Public
Change Control: Stable
Synopsis: Modifications to assign value to 'vntype' attribute of a job, when platform is Cray.
Details:

If platform is an actual Cray cluster or Cray ALPS simulator:
- Set vntype value as 'cray_compute'.

Interface: Server.submit()
Visibility: Public
Change Control: Stable
Synopsis: Modifications to consider aprun command if the platform is Cray.
Details:

If platform is an actual Cray cluster or Cray ALPS simulator:
- Prefix job executable with "aprun -B".
- If user is creating job script using 'create_script' inside test case then do not prefix "aprun -B", also user will have a full control over a job script same as how existing PTL works.
- Assign requested users home directory path to 'submit_dir'.