[Pin] unlocked status is not updated as expected

[Sujana2422]

Hi Metro SDK Team,

While using Pin.unlocked() to check the status of PinDialog, it returns true even when the wrong pin was entered.

The issue can be reproduced with sdkTestApp by the following steps

1. navigate to "Pin" and click on "show"
2. enter "0000" and click "enter"
3. click on "unlocked" and check the status on the console.
4. again click on "show" and enter "1234"
5. go back from the PinDialog by clicking backspace
6. click on "unlocked" and check the status on the console.

Actual behaviour: Pin.unlocked() returns true even the wrong pin was entered
Expected behaviour: Pin.unlocked() should return false when the wrong pin was entered

Identified the issue at the below line,
https://github.com/Metrological/metrological-sdk/blob/master/src/Pin/index.js#L33

Before rejecting, the unlocked status should be updated to false as shown below.

let submit = pin => {
  return new Promise((resolve, reject) => {
    if (pin.toString() === Settings.get('platform', 'pin', '0000').toString()) {
      unlocked = true
      resolve(unlocked)
    } else {
      unlocked = false
      reject('Incorrect pin')
    }
  })
}