Feature 3128 - Migrate installers to use subprocess module.
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Modified the ini installer to use the new subprocessSupport.py module in
place of the deprecated commands, system, spawn and popen python modules.
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The subprocessSupport.py module was also modfied for the following:
1. additional useShell argument in the method to allow the command to be
   executed through the shell.  This was needed in the cases where pipes,
   wildcards and other shell features were needed.  It previously was set
   to False thus not allowing this capability.  Added to the doc for this.
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2. Fixed a minor problem with the calling of the CalledProcessError
   Exception where the exitStatus was always being changed to zero.
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3. Also fixed a minor problem in the CalledProcessError class where it
   never output stderr from the call.

Note: the q/a installer was not modified at this time.
      A separate ticket should be generated for this.
Fix for multiple escape characters in classad values

Could not merge or cherry pick commit 0521bef0e8b05f5f80bf442b6ad80c77ba0a5e67 since v3 has refactored the code handling globals.  So, I manually applied the fix to the v2+ code base.
Merge branch 'branch_v2plus' into branch_v2plus_3128

Conflicts:
	install/manage-glideins
	install/services/Condor.py
Corrected pylint error
Bug #3446 - Installer not setting SHARED_PORT_MAX_WORKERS

Added SHARED_PORT_MAX_WORKERS = 1000 to the condor config when the
shared port option is in effect.

Files changed:
 - doc/components/condor.html
 - doc/components/condor_config.html
 - install/services/Condor.py
 - install/templates/02_gwms_factory_schedds.config
 - install/templates/02_gwms_schedds.config
Bug #3446 -  Installer not setting SHARED_PORT_MAX_WORKERS

Missed the q/a installer.
 - install/glideinWMS_install
Merge branch 'branch_v2plus' into branch_v2plus_3557