feature #3651: Add support for start script in context

If START_SCRIPT_BASE64 or START_SCRIPT is found in the context it is saved
to a temporary file and executed.

For OpenNebula ticket: http://dev.opennebula.org/issues/3651

base/etc/one-context.d/99-start-script

@@ -0,0 +1,24 @@
+#!/bin/bash
+
+MOUNT_DIR=/mnt
+TMP_DIR=/tmp/one-context-tmp
+TMP_FILE=$TMP_DIR/one-start-script
+START_SCRIPT_AVAILABLE=no
+
+mkdir -p $TMP_DIR
+
+if [ -n "$START_SCRIPT_BASE64" ]; then
+    echo -en "$START_SCRIPT_BASE64" | openssl enc -d -base64 -A > $TMP_FILE
+    START_SCRIPT_AVAILABLE=yes
+elif [ -n "$START_SCRIPT" ]; then
+    echo -en "$START_SCRIPT" > $TMP_FILE
+    START_SCRIPT_AVAILABLE=yes
+fi
+
+if [ "$START_SCRIPT_AVAILABLE" = "yes" ]; then
+    cd $MOUNT_DIR
+    chmod +x $TMP_FILE
+
+    $TMP_FILE
+fi
+