Fix building without IBus

It is not possible to successfully build cc-input-chooser.c when
HAVE_IBUS is undefined. Make sure that all code fragments which depends
on IBus are wrapped within ifdefs. Also remove the second include of
cc-ibus-utils.h since it is included twice and the first include is
already protected by an ifdef.

https://bugzilla.gnome.org/show_bug.cgi?id=730305