requirements-deb.txt: omit redundant packages

 * don't list packages pulled by ubuntu-minimal/ubuntu-standard metapackages
 * don't list the dependencies of build-essential metapackage
 * don't list nova, neutron, cinder, and glance dependencies

Skip the prerequisites of the following packages:

 * apache2
 * aptitude
 * cloud-init
 * corosync
 * cpu-checker
 * crda
 * discover
 * gdisk
 * git
 * grub-pc
 * guestmount
 * libgtk2.0 (not sure why we need libgtk itself)
 * libparse-debianchangelog-perl
 * libvte9 (why do we need this one?)
 * lksctp-tools
 * mysql
 * nodejs
 * novnc
 * pacemaker
 * python-utidylib
 * python-zmq
 * qemu-kvm
 * ruby-ohai
 * rabbitmq-server
 * tasksel
 * xauth
 * xinetd

Also added a script which helps to reduce dependencies.

Note: the obtained requirements-deb.txt still contains redundant and
extraneous entries, this issue will be handled later on.

Change-Id: Ic0d143a6f6e2eae01b721bae4fd3b6b748558c3b
Related-bug: #1383641
Merge "requirements-deb.txt: omit redundant packages"