Fix unit test failure

* Fixed enforcer plugin failure due to TestNG mismatch
versions.
* Bumping TestNG dependency to 6.8.8 triggered JUnit
assert class not found. So fixed all unit tests to use
TestNG asserts.
* Fixed the build failure for the module ios-grid
due to missing testng xml file.
Added fix in BaseUIAutomationCommandExecutor to escape unnecessary thread block when stop called during registration.
instruments shouldn't be put in the temporary file system.I should persist for long running servers.
adding cleanup when safari can't start
Added code to shutdown device if the device is already in booted state while erasing content and settings
Print .strings file path when unable to parse it
Update com.dd.plist and handle plist parsing error gracefully.