CTDB: drop sysconfig presence check during validate

There are two reasons to avoid this check:

• for ctdb versions prior to 4.9.0, the sysconfig file is generated by the resource agent start hook *after* ctdb_validate() is called.
• post 4.9.0 versions don't use the sysconfig file.

Signed-off-by: David Disseldorp <ddiss@suse.de>