build: add collie/farm/farm.h as noinst_HEADERS

Without this, 'make dist' would miss collie/farm/farm.h file.

Signed-off-by: Kai Zhang <kyle@zelin.io>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>
collie: correct help message for 'cluster snapshot'

Signed-off-by: Valerio Pachera <sirio81@gmail.com>
Signed-off-by: Liu Yuan <namei.unix@gmail.com>