Bug 2171: Wait for cloud init

Removes the explicit add of the GPG key from stage 3 as we
no longer use that key

Adds an explicit wait for cloud-init to finish before
proceeding with installation

Fixes bug 2171

Change-Id: I268efa1b0b322444d20ac9641745303b330bfd6a
Signed-off-by: Mark Beierl <mark.beierl@canonical.com>