ARTSPConnection: HTTP Authentication: Fix URI bounds

When parsing the DESCRIBE response of an RTSP server, the end of the
URI is one character too long. This causes an additional space to be
copied into the authorization header, which some servers reject.

Example:
* DESCRIBE rtsp://10.0.0.1:1234/Streaming/Channels/202 RTSP/1.0
* Authorization: Digest nonce="[nonce]", username="[user]", uri="rtsp://10.0.0.1:1234/Streaming/Channels/202 ", response="[res]"

Change-Id: Idb4e201578a2a2a0e4c59abad609816641a4dd99