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/node.go

@@ -201,6 +201,11 @@ func (n *node) write(p *page) {
 	}
 	p.count = uint16(len(n.inodes))
 
+	// Stop here if there are no items to write.
+	if p.count == 0 {
+		return
+	}
+
 	// Loop over each item and write it to the page.
 	b := (*[maxAllocSize]byte)(unsafe.Pointer(&p.ptr))[n.pageElementSize()*len(n.inodes):]
 	for i, item := range n.inodes {