Required: Unity configured to build to Android devices.
Repro steps:
1. Open the attached project
2. Build and run to Android device
3. Notice that the app is installed on the device but is not automatically opened
4. Check the console

Expected result: the app is installed and automatically opened on the device
Actual result: the app is installed but not opened; error thrown:
"CommandInvokationFailure: Unable to forward network traffic to device. Please make sure the Android SDK is installed and is properly configured in the Editor. See the Console for more details.
/home/unityqa/Android/Sdk/platform-tools/adb -s "efd3a563" forward "tcp:34999" "localabstract:Unity-com.foo.test"

stderr [error: cannot bind listener: Address already in use]
..."

Reproducible with: 5.6.3f1 (dev build only), 2017.1.0b3, 2017.2.0f3, 2017.4.13f1, 2018.2.11f1, 2018.3.0b5
Not reproducible with: 5.6.3f1 (non dev build)

Tested on: Ubuntu 16.04, Ubuntu 18.04
Issue not specific to a device

Workaround: Close Unity Editor and type the following in terminal: adb -s "xxx" forward "tcp:34999" "localabstract:Unity-com.foo.test"
(however, the port must be forwarded every time system after is restarted)