fix swapctl -A with DUIDs in /etc/fstab

[Stefan Sperling]

/etc/fstab:
736f610b58fed843.b none swap sw 0 0

# swapctl -A
swapctl: 736f610b58fed843.b: No such file or directory

With patch below:

# swapctl -A                    
swapctl: adding 736f610b58fed843.b as swap device at priority 0

Plug a tiny mem leak while here.  ok?

Index: swapctl.c
===================================================================
RCS file: /cvs/src/sbin/swapctl/swapctl.c,v
retrieving revision 1.17
diff -u -p -r1.17 swapctl.c
--- swapctl.c   26 Nov 2007 13:36:33 -0000      1.17
+++ swapctl.c   28 Dec 2010 20:33:47 -0000
@@ -395,9 +395,10 @@ do_fstab(void)
                                errx(1, "path too long");
                        if (system(cmd) != 0) {
                                warnx("%s: mount failed", fp->fs_spec);
+                               free((char *)spec);
                                continue;
                        }
-               } else {
+               } else if (spec[0] == '/') {
                        /*
                         * Determine blk-ness.  Don't even consider a
                         * mountpoint outside /dev as a block device.
@@ -419,6 +420,13 @@ do_fstab(void)
                        if (!S_ISREG(st.st_mode) &&
                            !S_ISBLK(st.st_mode))
                                continue;
+               } else if (strlen(spec) > 0) {
+                       /* Assume a DUID (block device). */
+                       if (rejecttype == S_IFBLK)
+                               continue;
+               } else {
+                       warnx("empty mountpoint");
+                       continue;
                }
 
                if (swapctl(SWAP_ON, spec, (int)priority) < 0) {