Fix mounting on FreeBSD

Currently, mounting on FreeBSD fails like this:

 mount_fusefs: ZZZZ<snip> on /mountpoint: No such file or directory

This happens because right after doing argv[a++] = fdnam it's
getting freed before calling execvp().

So move this free() call after execvp(). Also, when asprintf()
fails for fdnam, close device fd before calling exit().

lib/mount_bsd.c

@@ -222,6 +222,7 @@ static int fuse_mount_core(const char *mountpoint, const char *opts)
 				if(ret == -1)
 				{
 					perror("fuse: failed to assemble mount arguments");
+					close(fd);
 					exit(1);
 				}
 			}
@@ -232,14 +233,11 @@ static int fuse_mount_core(const char *mountpoint, const char *opts)
 				argv[a++] = opts;
 			}
 			argv[a++] = fdnam;
-
-			if(ret != -1)
-				free(fdnam);
-
 			argv[a++] = mountpoint;
 			argv[a++] = NULL;
 			execvp(mountprog, (char **) argv);
 			perror("fuse: failed to exec mount program");
+			free(fdnam);
 			exit(1);
 		}