Refactoring CompanionAdTestCase.java

##Rationale
It was suggested by @BCjwhisenant that my next move be to refactor **CompanionAdTestCase.java**, as, while it did work correctly, it was a little clunky and difficult to read and as someone who is still a beginner, learning to refactor code is an important skill.

##Changed Files
**OnceUxUiAutomatorBase.java**
* Changed *msecToPreroll* to 8000 to allow for less fails when the video takes too long to load.

**CompanionAdTestCase.java**
* Consolidated *testCompanionAd* and *testCompanionAdVanish* into one test
  * moved asserts to utility methods waitForCompanionAdCheck and waitForEndOfAdCheck
  * changed name of *testCompanionAd* to *testCompanionAdPresence*
  * removed *testCompanionAdVanish*
* Removed if-else statements from utility methods
* Changed *waitForCompanionAdCheck* and *waitForEndOfAdCheck* from booleans to voids
* Updated javadoc comments
* removed extraneous imports
Not a review comment as such, more a curiosity comment, but is this variable used to describe the time expected to wait between starting playback and the start of the preroll ad? (in this case, it would function as a sort of sleep() method).