Fix a double free issue with the Pickup dialplan application.

As part of the pickup process the connected line information is updated.
Part of this process does a shallow copy of the target channel's connected line
information to a local structure. Once complete the structure contents are freed.
As a result any information in the target channel's connected line information
structure is no longer valid. This change will now set the contents back to a clean
state so that the freeing of the target channel's connected line information structure
when the channel is destroyed will no longer try to double free things.

(closes issue #14839)
Reported by: lmsteffan


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@190217 65c4cc65-6c06-0410-ace0-fbb531ad65f3