Remove tlsCa option

The migration from phin to fetch in #755 was hampred by the lack of an
option to set the CA when using fetch.  This meant places that used phin
to talk to the controller with the tlsCa option could not be migrated to
use fetch.

Remove the tlsCa option to unblock this dependency. The replacement for
this option is to set the NODE_EXTRA_CA_CERTS environment variable to a
path to the certificate file instead, which works with fetch.

test/host.js

@@ -127,8 +127,8 @@ describe("Host testing", function() {
 					version: hostVersion,
 				}];
 				const hostConfig = new lib.HostConfig("host", { "host.version": hostVersion });
-				const hostConnector = new HostConnector(hostConfig, undefined, pluginInfos);
-				host = new Host(hostConnector, hostConfig, undefined, pluginInfos);
+				const hostConnector = new HostConnector(hostConfig, pluginInfos);
+				host = new Host(hostConnector, hostConfig, pluginInfos);
 			});
 			it("returns false when no changes are present", async function() {
 				host.pluginInfos[0].hostEntrypoint = true;