Improve parsing of cookie, thus removing trailing ;

[tking2]

This PR fixes #76 by correctly passing the correct cookie for TP_SESSIONID. A simple error in the code included a trailing semicolon at the end. It is apparent that legacy firmware versions ignored this, but P100 1.1.0 and P110 1.0.16 now treats this as invalid. May also resolve #74

[vladak]

Perhaps it should use http.cookies for even better robustness (ala https://gist.github.com/iximiuz/c8d16ce16759eddf6664)

[quinot]

Problem reproduced here and solution confirmed working, thanks @tking2

[sangimed]

Hello,

Anyone can merge the PR please ?

[pnuu]

Tested with L530, and indeed fixes #74 . Hope to get this merge ASAP!

[fishbigger]

So sorry I didn't get to merging this sooner. Looks good :)