Add armhf support.

ARM doesn't have a generic Linux image due to the soc-specific nature of Linux
kernels today, so we drop the manual installation of that package, replacing it
with a dist-upgrade instead. This involved tweaks to the dpkg and fedora
install-package scripts.

Change-Id: I97924b80ca87781307e1087b9fe4b18215770e84
Generate ssh hostkeys on first-boot.

cloud-init is expected to generate unique hostkeys on first
boot, but sometimes it doesn't.

This change ensures that hostkeys are always generated.
This change should be removed if the cloud-init problem is solved.

Change-Id: I7d7e05fbd12727992cf1aebec547ae0488e002ff
Merge "Generate ssh hostkeys on first-boot."
Fedora element allows root to sudo without TTY.

The root user tries to `sudo -u stack`, without a tty,
causing fedora+devstack images builds to fail in Jenkins.

Change-Id: Ia0a7fb315cf9bd17cf250e70dba06363a697c97c
Introduce the DIB_ namespace for build-time config.

Document the use of DIB_ as a prefix on environmental variables that can
be overridden at build time.

Introduce the first such variable by migrating IMAGE_SIZE to
DIB_IMAGE_SIZE.

Change-Id: Ie36b734991b913a23f37f2add47d470d7c1576e4
Merge "Introduce the DIB_ namespace for build-time config."
Migrate cloud image URL/Release options to DIB_.

This switches $CLOUD_IMAGES and $RELEASE to the DIB_ namespace so
they will survive future changes to the sanitisation of the build
environment.

Change-Id: I7dc2aa82fb9ef452705b080cc404f41046014f20
Allow build dir to be changed from /tmp

Adds an env var TMP_DIR which will override mktemp's default location.

Fixes bug 1168432

Change-Id: I60c63389bb2a639f948e7e96bf9aaea0ea73e27d
Grab the next available /dev/nbdX.

Change-Id: I6a2c8e58cdab889d747e870d0009f51bba0ff148
Merge "Grab the next available /dev/nbdX."
Merge "Migrate cloud image URL/Release options to DIB_."
Fix a small typo in fake init scripts.

Change-Id: Iaae4e8424ce2e87b0d19391fa2994042aed832e5
Fix Ubuntu image fetching.

Set a bash option which has been breaking cold builds due to an extended
glob pattern.

Change-Id: Ideab0fca057eb3744002ae137ac1f988b61bb560