fix: make ipfs.ping() options optional

Without this PR:

```console
$ npm test

...*snip*

     Uncaught TypeError: Cannot read property 'push' of null
      at /Users/alex/Documents/Workspaces/ipfs/js-ipfs/node_modules/pull-stream/sinks/collect.js:7:9
      at /Users/alex/Documents/Workspaces/ipfs/js-ipfs/node_modules/pull-stream/sinks/reduce.js:8:11
      at /Users/alex/Documents/Workspaces/ipfs/js-ipfs/node_modules/pull-stream/sinks/drain.js:24:37
      at callback (/Users/alex/Documents/Workspaces/ipfs/js-ipfs/node_modules/pull-pushable/index.js:84:5)
      at Function.push (/Users/alex/Documents/Workspaces/ipfs/js-ipfs/node_modules/pull-pushable/index.js:44:7)
      at libp2pNode.ping (src/core/components/ping-pull-stream.js:79:18)
      at _getPeerInfo (/Users/alex/Documents/Workspaces/ipfs/js-ipfs/node_modules/libp2p/src/index.js:339:7)
      at setImmediate (/Users/alex/Documents/Workspaces/ipfs/js-ipfs/node_modules/libp2p/src/get-peer-info.js:54:24)
      at Immediate.<anonymous> (/Users/alex/Documents/Workspaces/ipfs/js-ipfs/node_modules/async/internal/setImmediate.js:27:16)
```

Might resolve the second issue in #1616

Author: achingbrain

src/core/components/ping.js

@@ -5,6 +5,11 @@ const pull = require('pull-stream/pull')
 
 module.exports = function ping (self) {
   return promisify((peerId, opts, cb) => {
+    if (typeof opts === 'function') {
+      cb = opts
+      opts = {}
+    }
+
     pull(
       self.pingPullStream(peerId, opts),
       pull.collect(cb)

test/core/ping.spec.js

@@ -13,6 +13,10 @@ const isNode = require('detect-node')
 const expect = chai.expect
 chai.use(dirtyChai)
 const df = DaemonFactory.create({ exec: 'src/cli/bin.js' })
+const dfProc = DaemonFactory.create({
+  exec: require('../../'),
+  type: 'proc'
+})
 
 const config = {
   Bootstrap: [],
@@ -24,9 +28,10 @@ const config = {
   }
 }
 
-function spawnNode ({ dht = false }, cb) {
+function spawnNode ({ dht = false, type = 'js' }, cb) {
   const args = dht ? ['--enable-dht-experiment'] : []
-  df.spawn({
+  const factory = type === 'js' ? df : dfProc
+  factory.spawn({
     args,
     config,
     initOptions: { bits: 512 }
@@ -43,6 +48,61 @@ describe('ping', function () {
 
   if (!isNode) return
 
+  describe('in-process daemon', function () {
+    let ipfsdA
+    let ipfsdB
+    let bMultiaddr
+    let ipfsdBId
+
+    // Spawn nodes
+    before(function (done) {
+      this.timeout(60 * 1000)
+
+      series([
+        spawnNode.bind(null, { dht: false, type: 'proc' }),
+        spawnNode.bind(null, { dht: false })
+      ], (err, ipfsd) => {
+        expect(err).to.not.exist()
+        ipfsdA = ipfsd[0]
+        ipfsdB = ipfsd[1]
+        done()
+      })
+    })
+
+    // Get the peer info object
+    before(async function () {
+      this.timeout(60 * 1000)
+
+      const peerInfo = await ipfsdB.api.id()
+
+      ipfsdBId = peerInfo.id
+      bMultiaddr = peerInfo.addresses[0]
+    })
+
+    // Connect the nodes
+    before(async function () {
+      this.timeout(60 * 1000)
+      await ipfsdA.api.swarm.connect(bMultiaddr)
+    })
+
+    after(async () => {
+      if (!ipfsdA) return
+      await ipfsdA.stop()
+    })
+
+    after(async () => {
+      if (!ipfsdB) return
+      await ipfsdB.stop()
+    })
+
+    it('can ping via a promise without options', async () => {
+      const res = await ipfsdA.api.ping(ipfsdBId)
+
+      expect(res.length).to.be.ok()
+      expect(res[0].success).to.be.true()
+    })
+  })
+
   describe('DHT disabled', function () {
     // Without DHT nodes need to be previously connected
     let ipfsdA