vxlan: make option printing more consistent

vxlan: make option printing more consistent

Add new helper function print_bool_opt() which prints
with no prefix and use it for vxlan options.

If the option matches the expected default value,
it is not printed if in non JSON mode unless the details
setting is repeated.

Use a table for the vxlan options. This will change
the order of the printing of options.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>