integcli: resolve full path to docker binary

Setting dockerBinary to the full path of the Docker binary is a good
idea and this is now done in the test code.

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)

integration-cli/docker_test_vars.go

@@ -1,7 +1,9 @@
 package main
 
 import (
+	"fmt"
 	"os"
+	"os/exec"
 )
 
 // the docker binary to use
@@ -18,6 +20,15 @@ var workingDirectory string
 func init() {
 	if dockerBin := os.Getenv("DOCKER_BINARY"); dockerBin != "" {
 		dockerBinary = dockerBin
+	} else {
+		whichCmd := exec.Command("which", "docker")
+		out, _, err := runCommandWithOutput(whichCmd)
+		if err == nil {
+			dockerBinary = stripTrailingCharacters(out)
+		} else {
+			fmt.Printf("ERROR: couldn't resolve full path to the Docker binary")
+			os.Exit(1)
+		}
 	}
 	if registryImage := os.Getenv("REGISTRY_IMAGE"); registryImage != "" {
 		registryImageName = registryImage