Use /usr/bin/python2

Part of the effort to port FreeIPA to Arch Linux,
where Python 3 is the default.

FreeIPA hasn't been ported to Python 3, so the code must be modified to
run /usr/bin/python2

https://fedorahosted.org/freeipa/ticket/3438

Updated by pviktori@redhat.com
Increase Java stack size on s390 platforms

As reported in https://bugzilla.redhat.com/show_bug.cgi?id=1040576,
the default stack trace needs to be also increased on s390 platforms
to prevent rhino segfault.
cli.print_attribute: Convert values to strings

When output_for_cli was called directly, rather than for values
received through XML or JSON API, joining multiple values failed
on non-strings such as DN objects.

Convert output to strings before printing it out.