Tests: fix namespace error when compiling w/o cotire

If tests/unit_tests/main.h is not included after Kovri namespaces have been resolved, the compiler errors out.

Provide steps to reproduce. CI cannot reproduce nor can I.

Run: make COTIRE=0 tests

Produces the following errors (and more):

[ 83%] Linking CXX executable ../../kovri                                                                                                          
/home/oneiric/kovri/tests/unit_tests/client/api/i2p_control/parser.cc:43:11: error: use of undeclared identifier 'client'; did you mean            
      'kovri::client'?                                                                                                                             
  typedef client::I2PControlResponse Response;                                                                                                     
          ^~~~~~                                                                                                                                   
          kovri::client                                                                                                                            
/home/oneiric/kovri/src/client/../client/api/i2p_control/data.h:52:11: note: 'kovri::client' declared here                                         
namespace client                                                                                                                                   
          ^                                                                                                                                        
/home/oneiric/kovri/tests/unit_tests/client/api/i2p_control/parser.cc:44:11: error: use of undeclared identifier 'client'; did you mean            
      'kovri::client'?                                                                                                                             
  typedef client::I2PControlRequest Request;                                                                                                       
          ^~~~~~                                                                                                                                   
          kovri::client                                                                                                                            
/home/oneiric/kovri/src/client/../client/api/i2p_control/data.h:52:11: note: 'kovri::client' declared here                                         
namespace client

This PR fixes that problem.

@oneiric Do you have a status on this?

@seanfroth Ready to go.

assigned to @seanfroth

approved this merge request

merged