kong_api_authz build is broken

[JesseEstum]

The kong_api_authz module build appears to be broken on unit tests.

Steps to reproduce issue:

# from project root
cd kong_api_authz
make

Output:

[==========] Running tests from scanned files.
[----------] Global test environment setup.
[----------] Running tests from spec/kong/plugins/opa/access_spec.lua
[ RUN      ] spec/kong/plugins/opa/access_spec.lua @ 52: opa:access allow access
./src/kong/plugins/opa/access.lua:77: attempt to index field 'req' (a nil value)

stack traceback:
        ./src/kong/plugins/opa/access.lua:77: in function 'execute'
        spec/kong/plugins/opa/access_spec.lua:53: in function <spec/kong/plugins/opa/access_spec.lua:52>

[  ERROR   ] spec/kong/plugins/opa/access_spec.lua @ 52: opa:access allow access (2.54 ms)
[ RUN      ] spec/kong/plugins/opa/access_spec.lua @ 57: opa:access returns 403 when request is forbidden
./src/kong/plugins/opa/access.lua:77: attempt to index field 'req' (a nil value)

stack traceback:
        ./src/kong/plugins/opa/access.lua:77: in function 'execute'
        spec/kong/plugins/opa/access_spec.lua:60: in function <spec/kong/plugins/opa/access_spec.lua:57>

[  ERROR   ] spec/kong/plugins/opa/access_spec.lua @ 57: opa:access returns 403 when request is forbidden (1.97 ms)
[ RUN      ] spec/kong/plugins/opa/access_spec.lua @ 64: opa:access returns 500 on OPA server error or when not reachable
./src/kong/plugins/opa/access.lua:77: attempt to index field 'req' (a nil value)

stack traceback:
        ./src/kong/plugins/opa/access.lua:77: in function 'execute'
        spec/kong/plugins/opa/access_spec.lua:67: in function <spec/kong/plugins/opa/access_spec.lua:64>

[  ERROR   ] spec/kong/plugins/opa/access_spec.lua @ 64: opa:access returns 500 on OPA server error or when not reachable (2.30 ms)
[ RUN      ] spec/kong/plugins/opa/access_spec.lua @ 71: opa:access sends a request to the server defined in the configuration
./src/kong/plugins/opa/access.lua:77: attempt to index field 'req' (a nil value)

stack traceback:
        ./src/kong/plugins/opa/access.lua:77: in function 'execute'
        spec/kong/plugins/opa/access_spec.lua:78: in function <spec/kong/plugins/opa/access_spec.lua:71>

[  ERROR   ] spec/kong/plugins/opa/access_spec.lua @ 71: opa:access sends a request to the server defined in the configuration (2.24 ms)
[----------] 4 tests from spec/kong/plugins/opa/access_spec.lua (64.22 ms total)

[----------] Global test environment teardown.
[==========] 4 tests from 1 test file ran. (67.34 ms total)
[  PASSED  ] 0 tests.
[  ERROR   ] 4 errors, listed below:
[  ERROR   ] spec/kong/plugins/opa/access_spec.lua @ 52: opa:access allow access
[  ERROR   ] spec/kong/plugins/opa/access_spec.lua @ 57: opa:access returns 403 when request is forbidden
[  ERROR   ] spec/kong/plugins/opa/access_spec.lua @ 64: opa:access returns 500 on OPA server error or when not reachable
[  ERROR   ] spec/kong/plugins/opa/access_spec.lua @ 71: opa:access sends a request to the server defined in the configuration

 4 ERRORS

Error: test suite failed.

I will submit a pull request to fix this issue shortly.