test(mysql2): pin mysql2 to v1.6.1 (#652)

Version 1.6.2 has a bug.

This pin should be undone when the following issue is fixed:
sidorares/node-mysql2#869

Author: watson

.tav.yml

@@ -20,7 +20,7 @@ mysql:
     - node test/instrumentation/modules/mysql/mysql.js
     - node test/instrumentation/modules/mysql/pool-release-1.js
 mysql2:
-  versions: ^1.0.0
+  versions: '>=1.0.0 <1.6.2 || ^1.6.3' # v1.6.2 is broken: https://github.com/sidorares/node-mysql2/issues/869
   commands:
     - node test/instrumentation/modules/mysql2/mysql.js
     - node test/instrumentation/modules/mysql2/pool-release-1.js

package.json

@@ -122,7 +122,7 @@
     "mkdirp": "^0.5.0",
     "mongodb-core": "^3.0.2",
     "mysql": "^2.14.1",
-    "mysql2": "^1.5.1",
+    "mysql2": "1.6.1",
     "nyc": "^12.0.2",
     "once": "^1.4.0",
     "p-finally": "^1.0.0",