Fix handling of DNS names with '-' in them for sharenfs

An old FreeBSD bugzilla report PR#168158 notes that DNS
names with '-'s in them cannot be used for the sharenfs
property.  This patch fixes the parsing of these DNS names.
The only negative affect this patch might have is that,
if a user has incorrectly separated options with a '-'
the sharenfs setting will no longer work once this patch
is applied.

Reviewed by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Rick Macklem <rmacklem@uoguelph.ca>
Closes openzfs#16529

lib/libshare/os/freebsd/nfs.c

@@ -85,7 +85,9 @@ translate_opts(const char *shareopts, FILE *out)
 	strlcpy(oldopts, shareopts, sizeof (oldopts));
 	newopts[0] = '\0';
 	s = oldopts;
-	while ((o = strsep(&s, "-, ")) != NULL) {
+	while ((o = strsep(&s, ", ")) != NULL) {
+		if (o[0] == '-')
+			o++;
 		if (o[0] == '\0')
 			continue;
 		for (i = 0; i < ARRAY_SIZE(known_opts); ++i) {