mntent: exclude trailing newline from parsed field

When the pattern was changed from matching any whitespace to just
matching spaces and tabs, a newline started being appended to the
value of the matched field, if that field was a string. For example,
in a 4-field line, the mnt_opts field would have a newline on the end.

This happened because a newline is not a space or a tab, and so was
matched as part of the value before the end of the string was reached.
\n should therefore be added as a character that terminates a value.
This shouldn't interfere with the intention of the change to space and
tab only, as it was trying to make sure that other whitespace like
carriage returns, that should have been part of parsed values, were.

Fixes: f314e133

src/misc/mntent.c

@@ -81,7 +81,7 @@ struct mntent *getmntent_r(FILE *f, struct mntent *mnt, char *linebuf, int bufle
 		len = strlen(linebuf);
 		if (len > INT_MAX) continue;
 		for (i = 0; i < sizeof n / sizeof *n; i++) n[i] = len;
-		sscanf(linebuf, " %n%*[^ \t]%n %n%*[^ \t]%n %n%*[^ \t]%n %n%*[^ \t]%n %d %d",
+		sscanf(linebuf, " %n%*[^ \t\n]%n %n%*[^ \t\n]%n %n%*[^ \t\n]%n %n%*[^ \t\n]%n %d %d",
 			n, n+1, n+2, n+3, n+4, n+5, n+6, n+7,
 			&mnt->mnt_freq, &mnt->mnt_passno);
 	} while (linebuf[n[0]] == '#' || n[1]==len);