fsck_ufs: fix segfault with gjournal

The segfault was being hit in ckfini() (sbin/fsck_ffs/fsutil.c) while
attempting to traverse the buffer cache. The tail queue used for the
buffer cache was not initialized before dropping into gjournal_check().

Initialize the buffer cache before calling gjournal_check().

PR:             245907
Reviewed by:    jhb, mckusick
MFC after:      1 week
Differential Revision:  https://reviews.freebsd.org/D30537

sbin/fsck_ffs/main.c

@@ -309,6 +309,7 @@ checkfilesys(char *filesys)
 				exit(0);
 			}
 			if ((sblock.fs_flags & (FS_UNCLEAN | FS_NEEDSFSCK)) == 0) {
+				bufinit();
 				gjournal_check(filesys);
 				if (chkdoreload(mntp) == 0)
 					exit(0);