burnin: Get 'ignore_ssl' option from kamaki config

If '-k' flag is not given, try to retrieve it from kamaki's config file.
collectd: Read only the first line of the pid file

Since qemu doesn't truncate the pid file when it opens / creates it,
there's a chance that the pid file will contain more than one lines,
with truncated older PIDs. Read only the first line of the pid file, to
avoid an exception in the cpustats collectd plugin.
docs: Typo fixes in admin-guide