Impossible to run VCL tests due to a spurious backend declaration in example.vcl

Problem/Motivation

Authcache Varnish comes with docker based integration tests for the VCL shipping with authcache. Due to a spurious backend declaration those tests will fail with the following output:

**** v1    0.5 CLI RX| Message from VCC-compiler:\n
**** v1    0.5 CLI RX| Unused backend s1, defined:\n
**** v1    0.5 CLI RX| ('input' Line 2 Pos 9)\n
**** v1    0.5 CLI RX| backend s1 { .host = "127.0.0.1"; .port = "34125"; }\n
**** v1    0.5 CLI RX| --------##------------------------------------------\n
**** v1    0.5 CLI RX| \n
**** v1    0.5 CLI RX| Running VCC-compiler failed, exited with 2\n
**** v1    0.5 CLI RX| \n
**** v1    0.5 CLI RX| VCL compilation failed
---- v1    0.5 FAIL VCL does not compile
*    top   0.5 RESETTING after auc/fetch-0002-set-cookie-sess-key.vtc

Proposed resolution

Remove the backend declarations from the example.vcl file. Those are left-overs from manual testing.

Remaining tasks

User interface changes

API changes

Data model changes