Update tests and example to use the new libusb_init_context() function

This commit updates all test and example code to use the newer
libusb_init_context() function instead of libusb_init().

Signed-off-by: Nathan Hjelm <hjelmn@google.com>
[Tormod: Update umockdev.c as well]
Signed-off-by: Tormod Volden <debian.tormod@gmail.com>
11 files changed