Bugfix: make test case independent

Use www.taobao.com to replace senginx.test in dynamic_resolve.t

Signed-off-by: Paul Yang(InfoHunter) <paulyang.inf@gmail.com>
Bugfix: in ngx_http_upstream_dynamic_module

If fail_timeout is enabled and fallback action is specified
to either "stale" or "next", a segmentation fault would happen.

Signed-off-by: Paul Yang(InfoHunter) <paulyang.inf@gmail.com>
Merge pull request #499 from InfoHunter/dyn-dns

Bugfix: in ngx_http_upstream_dynamic_module
Merge pull request #498 from InfoHunter/master

Bugfix: make test case independent
Introduce a built-in variable: $normalized_request

When working with key-value store, such as memcached, we usually use URL
to generate unique key for each object.

But unfortunately, each URL may have several forms, for example:

1) http://abc.com/search?text=Hello+G%C3%BCnter#h1
2) http://ABC.COM/search?text=Hello+G%c3%bcnter#h1
3) HTTP://abc.com/search?text=Hello+G%C3%BCnter#h3

All above froms are refer to the same object. So we have to normalize URL
before generating object key.

As we known, URL syntax looks like:
 <scheme>://<user>:<password>@<host>:<port>/<path>;<params>?<query>#<frag>

The $normalized_request variable is the normalized form of URL, which will:
 - exclude #<frag> part from URL.
 - convert <scheme> and <host> to lower-case.
 - convert all escape characters(%nn) in <path> to upper-case.

Signed-off-by: Yunkai Zhang <qiushu.zyk@taobao.com>