tendril: Fix relative reference to favicon when not on root
tendril: Fix relative reference to favicon when not on root

When not on a top-dir url hierarchy, the icon load returns a 404,
not working, for example, on pages such as

https://tendril.wikimedia.org/host/view/db1074.eqiad.wmnet/3306

Use an absolute path, like the js loaded above.

Bug: T204110
Change-Id: Ief063d21f52536d25608744904e37d6b04800206

wikimedia/operations-software-tendril,wikimedia/operations-software-tendril,wikimedia/operations-software-tendril