Fix the LFI tests

[psiinon]

Some of the LFI test cases are failing, in that they cannot be exploited.

[psiinon]

All of the remaining broken LFI tests require \ in the payload.
Tomcat 9 rejects this as invalid: java.lang.IllegalArgumentException: Invalid character found in the request target.
There are various potential fixes .. but if the "fix" is too broad then the test is no longer specific enough...