Update boltdb dependency to fix golang 1.7 intermittent failures

We have a old boltdb/bolt, etcd has moved to newer boltdb, so we should
do the same. Specifically this change needs to be in our tree:
92410e0673

as this fixes intermittent issues we see in our CI runs. So in this
PR, we vendor the v1.3.0 version of boltdb/bolt.

Fixes #43973

vendor/github.com/boltdb/bolt/freelist.go

@@ -166,12 +166,16 @@ func (f *freelist) read(p *page) {
 	}
 
 	// Copy the list of page ids from the freelist.
-	ids := ((*[maxAllocSize]pgid)(unsafe.Pointer(&p.ptr)))[idx:count]
-	f.ids = make([]pgid, len(ids))
-	copy(f.ids, ids)
+	if count == 0 {
+		f.ids = nil
+	} else {
+		ids := ((*[maxAllocSize]pgid)(unsafe.Pointer(&p.ptr)))[idx:count]
+		f.ids = make([]pgid, len(ids))
+		copy(f.ids, ids)
 
-	// Make sure they're sorted.
-	sort.Sort(pgids(f.ids))
+		// Make sure they're sorted.
+		sort.Sort(pgids(f.ids))
+	}
 
 	// Rebuild the page cache.
 	f.reindex()
@@ -189,7 +193,9 @@ func (f *freelist) write(p *page) error {
 
 	// The page.count can only hold up to 64k elements so if we overflow that
 	// number then we handle it by putting the size in the first element.
-	if len(ids) < 0xFFFF {
+	if len(ids) == 0 {
+		p.count = uint16(len(ids))
+	} else if len(ids) < 0xFFFF {
 		p.count = uint16(len(ids))
 		copy(((*[maxAllocSize]pgid)(unsafe.Pointer(&p.ptr)))[:], ids)
 	} else {