Add conversion function from GCE storage units to kubernetes units.

cluster/gce/configure-vm.sh

@@ -308,12 +308,26 @@ EOF
     if [[ "${ENABLE_CLUSTER_REGISTRY}" == true && -n "${CLUSTER_REGISTRY_DISK}" ]]; then
       cat <<EOF >>/srv/salt-overlay/pillar/cluster-params.sls
 cluster_registry_disk_type: gce
-cluster_registry_disk_size: ${CLUSTER_REGISTRY_DISK_SIZE//GB/Gi}
+cluster_registry_disk_size: $(convert-bytes-gce-kube ${CLUSTER_REGISTRY_DISK_SIZE})
 cluster_registry_disk_name: ${CLUSTER_REGISTRY_DISK}
 EOF
     fi
 }
 
+# The job of this function is simple, but the basic regular expression syntax makes
+# this difficult to read. What we want to do is convert from [0-9]+B, KB, KiB, MB, etc
+# into [0-9]+, Ki, Mi, Gi, etc.
+# This is done in two steps:
+#   1. Convert from [0-9]+X?i?B into [0-9]X? (X denotes the prefix, ? means the field
+#      is optional.
+#   2. Attach an 'i' to the end of the string if we find a letter.
+# The two step process is needed to handle the edge case in which we want to convert
+# a raw byte count, as the result should be a simple number (e.g. 5B -> 5).
+function convert-bytes-gce-kube() {
+  local -r storage_space=$1
+  echo "${storage_space}" | sed -e 's/^\([0-9]\+\)\([A-Z]\)\?i\?B$/\1\2/g' -e 's/\([A-Z]\)$/\1i/'
+}
+
 # This should only happen on cluster initialization.
 #
 #  - Uses KUBE_PASSWORD and KUBE_USER to generate basic_auth.csv.