Fix lazy debuginfo loading on ppc64le

Fix lazy debuginfo loading on ppc64le

Lazy debuginfo loading introduced in commit 60f7e89ba32 assumed that
either describe_IP or find_DiCfSI will be called before stacktrace
printing.  describe_IP and find_DiCfSI cause debuginfo to be lazily
loaded before symtab lookup occurs during stacktraces.

However this assumption does not hold true on ppc64le, resulting
in debuginfo failing to load in time for stacktraces.  Fix this
by loading debuginfo during get_StackTrace_wrk on ppc arches.