Setting the nova_console_keymap variable to 'en-us' breaks the
keyboard input for novnc consoles. It's recommended to let vnc
automatically select the correct keymap.
This patch removes the keymap variables from the `nova.conf`
templates and their default values.
Closes-bug: 1691791
Change-Id: I049ad6db2198dc8d0fae04160486c5ba6f7f36f1