dblink._protect: disable config protect for identical files (531854)

Since commit 02417188225758b1822d176abd8902a92300a371, config
protection was triggered for identical files if
config-protect-if-modified was not enabled in FEATURES. Fix it
to skip config protection in this case.

Fixes: 024171882257 ("CONFIG_PROTECT: protect symlinks, bug #485598")
X-Gentoo-Bug: 531854
X-Gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=531854
Acked-by: Brian Dolbec <dolsen@gentoo.org>