CredentialCache does not handle encoded slashes (%2f) correctly

When comparing prefixes for potential match, CredentialCache does not take into acount that some characters may be %-encoded, for example.

http://host/a/b/c

and

http://host/a%2fb/c

are equivalent, but will the second will not reuse the credential for `a/b` path on the host.

Start by locating CredentialCache and read the prefix-comparison logic described in the issue. Reproduce the examples with /a/b/c and /a%2fb/c, then verify that the encoded-slash form reuses the credential for the a/b path without changing unrelated prefix matches.

Written by the indexing model from the issue text.