Remove unexpected default cert path in DockerHost

`DockerHost.fromEnv()` shouldn't have a cert path if the
`DOCKER_CERT_PATH` env var isn't set.

Author: davidxia

src/main/java/com/spotify/docker/client/DefaultDockerClient.java

@@ -125,6 +125,7 @@
 import javax.ws.rs.core.MediaType;
 import javax.ws.rs.core.Response;
 
+import static com.google.common.base.MoreObjects.firstNonNull;
 import static com.google.common.base.Optional.fromNullable;
 import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.base.Preconditions.checkNotNull;
@@ -1681,7 +1682,8 @@ public static Builder builder() {
    */
   public static Builder fromEnv() throws DockerCertificateException {
     final String endpoint = DockerHost.endpointFromEnv();
-    final Path dockerCertPath = Paths.get(DockerHost.certPathFromEnv());
+    final Path dockerCertPath = Paths.get(firstNonNull(DockerHost.certPathFromEnv(),
+                                                       DockerHost.defaultCertPath()));
 
     final Builder builder = new Builder();
 

src/main/java/com/spotify/docker/client/DockerHost.java

@@ -213,7 +213,7 @@ static String defaultCertPath() {
   }
 
   static String certPathFromEnv() {
-    return firstNonNull(systemDelegate.getenv("DOCKER_CERT_PATH"), defaultCertPath());
+    return systemDelegate.getenv("DOCKER_CERT_PATH");
   }
 
   @Override

src/test/java/com/spotify/docker/client/DockerHostTest.java

@@ -98,7 +98,7 @@ public void testCertPathFromEnv() throws Exception {
     DockerHost.setSystemDelegate(systemDelegate);
 
     assertThat(DockerHost.certPathFromEnv(), equalTo("foo"));
-    assertThat(DockerHost.certPathFromEnv(), equalTo("bar/.docker"));
+    assertThat(DockerHost.certPathFromEnv(), equalTo(null));
   }
 
   @Test
@@ -151,7 +151,7 @@ public void testFromEnv() throws Exception {
     final String dockerHostEnvVar = DockerHost.defaultDockerEndpoint();
     final boolean isUnixSocket = dockerHostEnvVar.startsWith("unix://");
     final URI dockerHostUri = new URI(dockerHostEnvVar);
-    final String dockerCertPathEnvVar = DockerHost.defaultCertPath();
+    final String dockerCertPathEnvVar = null;
 
     final String dockerHostAndPort;
     final URI dockerHostHttpUri;