bp:MB-8536: tidied redundant tasks in cbcollect_info

This is clean backport

Perticularly there's no need to invoke netstat -an[p] twice and no
need to ls membase directories twice. Also as pointed out in the
ticket we grab syslogs separately so there's no need to cat them.

Change-Id: I111c0f4f64190cbe678b96936d89dc8390efca70
Orig-Reviewed-on: http://review.couchbase.org/29441
Reviewed-on: http://review.couchbase.org/29516
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>