examples: testlibusb: Always print VID and PID in addition to strings

examples: testlibusb: Always print VID and PID in addition to strings

Previously the program would only print the VID when the manufacturer
string is unavailable and the PID when the product string is
unavailable. Change this to print the VID and PID unconditionally and
print the manufacturer and product strings similar to how the serial
number string is being printed. In addition, line up the string values
with the rest of the output.

Signed-off-by: Chris Dickens <christopher.a.dickens@gmail.com>