These are the last two internal use cases for URLBuilder.  And replacing
them makes my IDE happy.  Both are similar to the create case but
different.

InboundRewriteRuleAdaptor needs the encoding.
RewriteViewHandler needs to merge two query strings.

If we send an invalid URL to the URI parser, it falls over and fails.
But apparently we are supposed to accept and fix rules that produce
invalid URLs.  So encode URL before we try to parse it.

String.join did not exist prior to Java 8.  So implement manually with
StringBuilder.

Use Pattern.quote to escape the question mark and use it literally.

Since both pathEncoded and pathDecoded decode the string, use
pathDecoded so people will know what's happening.

As this test is not failing locally and not producing useful information
on Travis, adding a message to the failing assertion.

We cast event to HttpServletRewrite before getting the inbound address.
We do not need to keep doing it, as we have the cast version stored.