Going back to setting default value for variable.

Put the default value of INSTALL_DEBIAN_INIT_SCRIPT in curly braces.
This worked on Ubuntu, but the "x$foo" method didn't.
Added "set +e" blocks for Ubuntu tasks.

When installing init scripts and [re]starting services, set -e causes
the script to bail.  This patch adds set +e / set -e blocks to prevent
undesired exiting.
Merge branch 'disable_auto_exit_for_some_tasks' into baremetal