Use Set (again) for enumerating MvcEndpoints

This reverts a change that I assume was orphaned from work in
progress to address #1353, but is no longer needed. Anyway
there is no reason to restrict MvcEndpoints to be unique by
path since they can declare their own @RequestMappings
(and if there are duplicates they will be detected when those
are scanned).

Fixes gh-1911

spring-boot-actuator/src/test/java/org/springframework/boot/actuate/endpoint/mvc/EndpointHandlerMappingTests.java

@@ -133,6 +133,21 @@ public class EndpointHandlerMappingTests {
 				nullValue());
 	}
 
+	@Test
+	public void duplicatePath() throws Exception {
+		TestMvcEndpoint endpoint = new TestMvcEndpoint(new TestEndpoint("/a"));
+		TestActionEndpoint other = new TestActionEndpoint(new TestEndpoint("/a"));
+		EndpointHandlerMapping mapping = new EndpointHandlerMapping(Arrays.asList(
+				endpoint, other));
+		mapping.setDisabled(true);
+		mapping.setApplicationContext(this.context);
+		mapping.afterPropertiesSet();
+		assertThat(mapping.getHandler(new MockHttpServletRequest("GET", "/a")),
+				nullValue());
+		assertThat(mapping.getHandler(new MockHttpServletRequest("POST", "/a")),
+				nullValue());
+	}
+
 	private static class TestEndpoint extends AbstractEndpoint<Object> {
 
 		public TestEndpoint(String path) {