test: set chain to mainnet after testing in key_io_tests

Rationale:
    Sadly some other tests depends on the chain being mainnet without actually
    setting it to mainnet themselves. Which leads to weird test suite
    failures.

src/test/key_io_tests.cpp

@@ -78,6 +78,8 @@ BOOST_AUTO_TEST_CASE(key_io_valid_parse)
             BOOST_CHECK_MESSAGE(!privkey.IsValid(), "IsValid pubkey as privkey:" + strTest);
         }
     }
+
+    SelectParams(CBaseChainParams::MAIN);
 }
 
 // Goal: check that generated keys match test vectors
@@ -144,6 +146,8 @@ BOOST_AUTO_TEST_CASE(key_io_invalid)
             BOOST_CHECK_MESSAGE(!privkey.IsValid(), "IsValid privkey in mainnet:" + strTest);
         }
     }
+
+    SelectParams(CBaseChainParams::MAIN);
 }
 
 BOOST_AUTO_TEST_SUITE_END()