silently clear buckets when changing disk path in wizard.MB-4548
silently clear buckets when changing disk path in wizard.MB-4548

This can only happen via 'Back' in wizard. And in this case just
losing data seems ok.

Note: we're going to implement sample docs loading. With sample docs
loading we'll need some other fix to this problem.

Change-Id: I05d48a0000c721c2bbae5d2dcef4ccddf830a38a
Reviewed-on: http://review.couchbase.org/11924
Reviewed-by: Dale Harvey <491ccac09a36ad1e38b698f273b84fd8efc31071@arandomurl.com>
Tested-by: Dale Harvey <491ccac09a36ad1e38b698f273b84fd8efc31071@arandomurl.com>

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