Looking at your Appium log, I think the version of Chromedriver you are using is not matched to the version of Chrome on your test device:
2018-07-18 07:08:51:146 - info: [debug] [Chromedriver] Changed state to 'stopped’
2018-07-18 07:08:51:146 - error: [Chromedriver] Error: Failed to start Chromedriver session: An error occurred (Original error: chrome not reachable
2018-07-18 07:08:51:146 - error: [Chromedriver] (Driver info: chromedriver=2.28.455506 (18f6627e265f442aeec9b6661a49fe819aeeea1f),platapplication=Linux 4.15.0-24-generic x86_64))
“chrome not reachable” is the message I get when the versions are mismatched and chromedriver 2.28 is pretty old at this point so I would imagine that your device’s Chrome browser is updated but the driver is not… Fire up Chrome on your Android to see what version you have and the go here to get the appropriate chromedriver:
There is a folder for the updated chromedriver in Appium’s node_modules folder.
Good Luck!