Update cinder content for Juno

I updated the cinder content in the installation guide for Juno
as follows:

1) Add the python-oslo-db package because the openstack-cinder
   package depends on it, but does not install it.
2) Install the lvm2 package to remove assumption that
   distributions install it by default.
3) Enable and start LVM metadata service prior to volume
   creation.
4) Rename openstack-cinder-volume package to openstack-cinder.

This patch originates from testing on Fedora and applies to
installations on RHEL/CentOS/Fedora.

Change-Id: Idc2dbf8e60b9e79f36c3e1882fc98b61e5fddb53
Merge "Update cinder content for Juno"