Possible cache issue with demo endpoint

[rowanmanning]

[originally reported by @AlbertoElias]

OBT has a bug where it builds demos indentically when building multiple of them that share the same template. Build service shouldn't have this issue as it only compiles one demo at a time, but with o-header, it generates the core demo for the enhanced one.

[Limess]

Tried to reproduce this locally with o-header in integration tests and couldn't:

		it('should not cache demo templates for the same component when built concurrently', function() {
			const testModule = 'o-header';
			const request1 = new Promise((resolve, reject) => {
				request(this.app)
					.get(`/v2/demos/${testModule}/main`)
					.set('Connection', 'close')
					.end(function(err, res) {
						if (err) return reject(err);
						resolve(res.text);
					});
			});

			const request2 = new Promise((resolve, reject) => {
				request(this.app)
					.get(`/v2/demos/${testModule}/mega-menu`)
					.set('Connection', 'close')
					.end(function(err, res) {
						if (err) return reject(err);
						resolve(res.text);
					});
			});

			return Promise.all([request1, request2])
			.then(([response1, response2]) => {
					assert.notDeepEqual(response1, response2);
				});
		});

		it('should not cache demo templates for the same component when built in serial', function() {
			const testModule = 'o-header';
			const request1 = new Promise((resolve, reject) => {
				request(this.app)
					.get(`/v2/demos/${testModule}/main`)
					.set('Connection', 'close')
					.end(function(err, res) {
						if (err) return reject(err);
						resolve(res.text);
					});
			});

			const request2 = new Promise((resolve, reject) => {
				request(this.app)
					.get(`/v2/demos/${testModule}/mega-menu`)
					.set('Connection', 'close')
					.end(function(err, res) {
						if (err) return reject(err);
						resolve(res.text);
					});
			});

			return request1.then((response1) => {
				return request2
					.then((response2) => {
						assert.notDeepEqual(response1, response2);
					});
			});
		});