analyzer: Have exited processes read all data

[mattnibs]

This commit changes the behavior for analyzer processes so that processes that have successfully exited without reading all the data will continue to consume data from the byte stream insteading of returning an error and putting a stop to the copy goroutine.

Closes #331

[philrz]

tl;dr

This is a functional 👍 for me!

Details

I pointed my Zui at the Brimcap commit from this branch and tested it out with the pcaps I mentioned in #331 comments and saw the improvements expected in both cases.

1. For the one in Analyzers that exit clean without reading input until EOF #331 (comment), the error changes from this incorrect one:

to this accurate one:

and that latter error message will go away entirely when the Zeek v6.0.3-based artifact is in use since that has support for this link type.

2. For the one in Analyzers that exit clean without reading input until EOF #331 (comment), it goes from showing this incorrect error message:

to a successful import:

i.e., Suricata quietly refused to do anything with this pcap since it doesn't support the link layer protocol, but since it returned an exit code of 0 the Zui user gets only Zeek events. This seems like a fine place to be while we wait to see if the Suricata people ever catch up and address the existing issues.