[DEV-1038] Cloud init lvm growpart (#46)

* added cloud-init-growpart-lvm element

Author: g0rgamesh

elements/cloud-init-growpart-lvm/README.rst

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+=============
+cloud-init-growpart-lvm
+=============
+
+This element enables growpart for OS images with LVM.
+To enable this element simply include it in the elements list.
+
+* ``DIB_CLOUD_INIT_GROWPART_DEVICES`` list of partition names that needs to be 
+    populated in order for cloud-init to grow it. Populating it is mandatory.
+
+Dependencies:
+* ``/usr/bin/growpart`` is needed on the system in order to grow the partition.
+    However it is part of different packages depending on linux family. That
+    is already taken care of by package-installs.

elements/cloud-init-growpart-lvm/element-deps

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+pkg-map
+package-installs

elements/cloud-init-growpart-lvm/package-installs.yaml

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+growpart_package:

elements/cloud-init-growpart-lvm/pkg-map

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+{
+  "family": {
+    "redhat": {
+      "growpart_package": "cloud-utils-growpart"
+    },
+    "debian": {
+      "growpart_package": "cloud-guest-utils"
+    }
+  }
+}

elements/cloud-init-growpart-lvm/post-install.d/55-growpart-lvm

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+#!/bin/bash
+
+if [ ${DIB_DEBUG_TRACE:-1} -gt 0 ]; then
+    set -x
+fi
+set -euo pipefail
+
+if [[ -n ${DIB_CLOUD_INIT_GROWPART_DEVICES} ]]; then
+    if [ -d /etc/cloud/cloud.cfg.d ]; then
+        cat > /etc/cloud/cloud.cfg.d/55-growpart-lvm.cfg <<EOF
+#cloud-config
+growpart:
+  mode: auto
+  devices: $DIB_CLOUD_INIT_GROWPART_DEVICES
+  ignore_growroot_disabled: false
+EOF
+    fi
+else
+    echo "You must set the device list: \"$DIB_CLOUD_INIT_GROWPART_DEVICES\"."
+    exit 1
+fi