check for target bucket validness does not work for capi replication

XDCR periodically checks if target bucket is still valid. This check stopped working for capi replications after the fix for MB-20230 in 4.6, becasue the path that we use to connect to target, pools/default/b/, is not supported by elastic search.

This issue can be fixed by a one-line change - change the path used to connect to capi target. We are still re-visiting all connections to target, though, and may decide not to connect to target at all. Leaving this issue open for now