Fix menu button margins.

Make sure the button is center aligned to the shutter and mode switcher
buttons.

Change-Id: I66c26c94fa7a43df57b9df0bcfe79dc60e4d9c6c
Merge "Fix menu button margins." into cm-11.0
Merge branch 'cm-11.0' of https://github.com/CyanogenMod/android_packages_apps_Camera2 into cm-11.0