Fix output directory deletion logic
Fix output directory deletion logic

The intention was to prevent accidental source content data loss by
skipping output directory deletion if the output directory is a parent
of the source content directory. But the previous implementation did so
by checking path *strings*, resulting in scenarios where the following
settings would erroneously skip deletion of the output directory:

PATH = "/repo/docs-src/content"
OUTPUT_PATH = "/repo/docs"

The output directory should have been deleted but wasn't because the
PATH string contains "/repo/docs". This change eschews string comparison
and instead compares actual paths to ensure that the output path is not
a parent of the source content directory.

ingwinlu/pelican,avaris/pelican,getpelican/pelican,farseerfc/pelican,ingwinlu/pelican,avaris/pelican,farseerfc/pelican,getpelican/pelican