CCBC-537: cancel_http_request should call request_finish
CCBC-537: cancel_http_request should call request_finish

This fixes some bugs where the request wouldn't be decremented.

Change-Id: If27026fde886983a1820612e2ffd8ba75ad7e8ae
Reviewed-on: http://review.couchbase.org/42614
Reviewed-by: Sergey Avseyev <87f6d5e4fd3644c3c20800cde7fd3ad1569370b3@gmail.com>
Tested-by: Mark Nunberg <e7d42768707bf23038325b0b68d4b577e5f6064a@haskalah.org>

maxim-ky/libcouchbase,couchbase/libcouchbase,avsej/libcouchbase,signmotion/libcouchbase,PureSwift/libcouchbase,PureSwift/libcouchbase,mody/libcouchbase,avsej/libcouchbase,couchbase/libcouchbase,mody/libcouchbase,maxim-ky/libcouchbase,senthilkumaranb/libcouchbase,senthilkumaranb/libcouchbase,kojiromike/libcouchbase,couchbase/libcouchbase,avsej/libcouchbase,maxim-ky/libcouchbase,kojiromike/libcouchbase,signmotion/libcouchbase,mody/libcouchbase,PureSwift/libcouchbase,avsej/libcouchbase,senthilkumaranb/libcouchbase,couchbase/libcouchbase,avsej/libcouchbase,maxim-ky/libcouchbase,kojiromike/libcouchbase,mnunberg/libcouchbase,couchbase/libcouchbase,signmotion/libcouchbase,PureSwift/libcouchbase,mnunberg/libcouchbase,mody/libcouchbase,mnunberg/libcouchbase,couchbase/libcouchbase,signmotion/libcouchbase,senthilkumaranb/libcouchbase,couchbase/libcouchbase,mnunberg/libcouchbase,avsej/libcouchbase,mnunberg/libcouchbase,avsej/libcouchbase,kojiromike/libcouchbase