trusted launcher is not passing environment to local jobs executed as data source

This happened if plainbox-provider-certification-server and plainbox-autostart-server are used. It can also be reproduced by running 'checkbox sru' using sudo.

- install plainbox plainbox-provider-certification-server
- Prepare minimal whitelist as shown below
- sudo plainbox sru -w /path/to/minimal.whitelist

Expected:
- memory/info passes (it's the most basic memory test)

Actual:
- memory/info fails
- Trace as shown below

When plainbox uses the trusted launcher controller to execute a generated job that runs as root, the trusted launcher does not obtain environment specific to the job generator.

Minimal whitelist:
__memory__
memory/info

Trace:
cat: /jobs/memory.txt?(.in): No such file or directory
Traceback (most recent call last):
  File "/usr/bin/plainbox-trusted-launcher-1", line 9, in <module>
    load_entry_point('plainbox==0.4.dev', 'console_scripts', 'plainbox-trusted-launcher-1')()
  File "/usr/lib/python3/dist-packages/plainbox/impl/secure/launcher1.py", line 168, in main
    launcher.add_job_list(launcher.run_local_job(ns.via))
  File "/usr/lib/python3/dist-packages/plainbox/impl/secure/launcher1.py", line 88, in run_local_job
    output = subprocess.check_output(cmd, universal_newlines=True)
  File "/usr/lib/python3.3/subprocess.py", line 586, in check_output
    raise CalledProcessError(retcode, process.args, output=output)
subprocess.CalledProcessError: Command '['bash', '-c', 'shopt -s extglob\ncat $CHECKBOX_SHARE/jobs/memory.txt?(.in)']' returned non-zero exit status 1