Update jenkins::slave manifest to support Red Hat.

Adds a new jenkins::params module where we set parameters based on
the operating system name.

Updates the jenkins::slave module so that it makes use of distro specific
parameters via jenkins::params. In general almost all of the previously
installed packages are installed in the same fashion via the new param
files. The following special cases are handled via inline conditionals
in the jenkins::slave manifest:

 1) Ubuntu installs the 'build-essential' meta package. Since other
 distros don't necissarily have an equivilant package name we have to
 do this manually. On RHEL we yum install the 'Development tools'
 package group in a similar fashion.

 2) There aren't currently RHEL packages for maven and python3. I think
 this is probably Okay since our initial target for RHEL in openstack-ci
 is to be able to run unit tests which shouldn't require these.

 3) Lastly we exclude the sysctl.d ptrace.conf on RHEL since it doesn't
 currently support sysctl conf.d directory files. This is probably Okay
 as well since the initial target for this file was temporary and only
 to help debug a Glance unit test failure.

Change-Id: Ic46bc63ade3aab54a4381ca0c99fa03ac9dd59e2
Reviewed-on: https://review.openstack.org/18906
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Approved: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins