[uri] Apply URI decoding for all parsed URIs

The various early-exit paths in parse_uri() accidentally bypass the
URI field decoding.  The result is that opaque or relative URIs do not
undergo URI field decoding, resulting in double-encoding when the URIs
are subsequently used.  For example:

  #!ipxe
  set mac ${macstring}
  imgfetch /boot/by-mac/${mac:uristring}

would result in an HTTP GET such as

  GET /boot/by-mac/00%253A0c%253A29%253Ac5%253A39%253Aa1 HTTP/1.1

rather than the expected

  GET /boot/by-mac/00%3A0c%3A29%3Ac5%3A39%3Aa1 HTTP/1.1

Fix by ensuring that URI decoding is always applied regardless of the
URI format.

Reported-by: Andrew Widdersheim <awiddersheim@inetu.net>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/core/uri.c

@@ -419,11 +419,11 @@ struct uri * parse_uri ( const char *uri_string ) {
 		uri->port = tmp;
 	}
 
+ done:
 	/* Decode fields in-place */
 	for ( field = 0 ; field < URI_FIELDS ; field++ )
 		uri_decode_inplace ( uri, field );
 
- done:
 	DBGC ( uri, "URI parsed \"%s\" to", uri_string );
 	uri_dump ( uri );
 	DBGC ( uri, "\n" );