Resolves: bug 425849
    Bug Description: migrate-ds-admin.pl spins at 100% cpu
    Reviewed by: nkinder (Thanks!)
    Fix Description: It was spinning because inst_dir was not being set, so it kept trying to find the parent directory of a non-existent directory.  In migration, the old instance has no instance dir - we will fill that in during instance creation, so just skip it if not set.  I also found and fixed another bug in migration with the usage of file_name_is_absolute - have to use the full module name and function name.
    Platforms tested: RHEL4 32bit and 64bit
    Flag Day: no
    Doc impact: no
    QA impact: should be covered by regular nightly and manual testing
    New Tests integrated into TET: none