LTI broken when using long activity name (regression)

When using a long activity name, the resource_link_title in the LTI launch request is modified and the oAuth signature is wrong.
 
 This is a regression from MDL-58770

https://tracker.moodle.org/browse/MDL-58770
 
 Steps to reproduce:
 1. Install Moodle 3.3.1
 2. Add External Tool Provider:
 Launch URL: http://lti.tools/test/tc.php
 Consumer Key: jisc.ac.uk
 Shared secret: secret
 3. Create activity with the external tool. Use a short name "aaa".
 4. Verify that the request summary is valid and says:
 basic-lti-launch-request message request is valid.
 5. Change the activity name to
 "a aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa a a a a a a a a a a a a a a a a a a a a aa a a aa"
 6. Try to launch the activity and see that the request summary is now:
 Could not validate request: OAuth signature check failed - perhaps an incorrect secret or timestamp.
 
 Bad commit found with git bisect:
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 22227b7701d20e67784ce1e29606f19ad08e0bbf is the first bad commit
 commit 22227b7701d20e67784ce1e29606f19ad08e0bbf
 Author: Stephen Vickers <github@spvickers.freeserve.co.uk>
 Date:   Mon May 1 21:10:40 2017 +0100

    MDL-58770 mod_lti: Strip HTML from parameters

    Remove HTML tags from parameters which should be plain text.

:040000 040000 f3a7b2c667a981feaeda48fcfca0966991a0a4c4 72ee91c80fb15c128474517d53784868836ecaed M mod

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