Adding retries to install-ssmsmin and install-sqltoolsservice for download/install failures (#6880)

* Changes to enable retry for Service downloader.
* removing 'enabled' flag from the "retry" config.
*  use 0.1.7 release of service-downloader which enables the retry feature.

package.json

@@ -92,13 +92,13 @@
     "@types/keytar": "^4.4.0",
     "@types/mocha": "2.2.39",
     "@types/node": "^10.12.12",
+    "@types/plotly.js": "^1.44.9",
     "@types/sanitize-html": "^1.18.2",
     "@types/semver": "^5.5.0",
     "@types/should": "^13.0.0",
     "@types/sinon": "^1.16.36",
     "@types/webpack": "^4.4.10",
     "@types/winreg": "^1.2.30",
-    "@types/plotly.js": "^1.44.9",
     "ansi-colors": "^3.2.3",
     "asar": "^0.14.0",
     "chromium-pickle-js": "^0.2.0",