Bug 16749: Adjustments for koha-plack

Bug 16749: Adjustments for koha-plack

[1] Use run_safe_xmlstarlet for plack workers and requests
[2] Simplify adjust_paths. The lazy export statement is actually enough to
    replace adjust_paths by one direct call to adjust_paths_dev_install.

Test plan:
[1] Copy koha-functions.sh and koha-plack:
    cp [YOUR_PATH]/debian/scripts/koha-functions.sh /usr/share/koha/bin/
    cp [YOUR_PATH]/debian/scripts/koha-plack /usr/sbin/
    where YOUR_PATH might well be /home/vagrant/kohaclone.
[2] Make sure that you have dev_install in koha-conf.
    Stop and start koha-plack. Verify with ps aux|grep plack.
[3] Rename dev_install to nodev_install (in start and end tag).
    Now stop/start koha-plack. Verify with ps aux|grep plack.
[4] Change plack_requests to 51 in your koha-conf.
    Restart Plack and check that you see 51 in ps aux|grep plack.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Tested on Jessie (Debian VM and Kohadevbox)

Signed-off-by: Mirko Tietgen <mirko@abunchofthings.net>
Tested in a package installation of master+16749

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>