No option to cancel the contact adding manually

[Jin]

Description:
There is no option for users to cancel the contact adding process.

Reproduce Steps:
    a) Launch Telegram
    b) Select "Contacts" in settings
    c) Press the button in top right to add the contact
    d) Select "Enter Details" to add manually
    e) Observe the Telegram UI

Expected Result:
There is a back key action for users to cancel the contact adding page.

Actual Result:
There is no option to cancel contact adding.

Occurrence:
10/10 (100%)

Software Information:
    com.ubuntu.telegram (2.2.26.0)

Hardware Information:
    current build number: 480
    device name: mako
    channel: ubuntu-touch/rc-proposed/ubuntu
    last update: 2016-07-07 11:36:27
    version version: 480
    version ubuntu: 20160706.1
    version device: 20160401.1
    version custom: 20160706.1