MB-10086: [cbcollect_info] added support for manual uploading

I.e. when folks cannot use ns_server's cluster-wide collectinfo
gathering and cannot use curl directly.

Change-Id: Ie2bc47ef58dc2e314515c824febbd28eb3cd299b
Reviewed-on: http://review.couchbase.org/38054
Tested-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>
Reviewed-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>