Parametrize target_dir for the timestamp

The default location where we write timestamp files is
/tmp, however, this location does not work for all systems -
/tmp directory cannot be expected to persist across reboots
of an instance.

This commit allows users to set their preferred location and
override the default (/tmp) target dir.

Closes-Bug: #2051268
Change-Id: Id23ae70001525c8eb95d6baf0aca2b4d399e63a1
3 files changed