Revert "Revert "Fixed possible mount abuse after leaving bg""

This reverts commit 7d5077078097812ef20cc1bbeb4f6bfe40f3fb26.
[TW354] - Core/Battleground: Solve some warnings added in https://github.com/TrueWoW/TrinityCore/commit/10bf6dbb0da76f086caafb18cf7d48cbdc3787a8 caused by uninitialized variables and clear some redundancy
Merge pull request #2 from TrueWoW/master

pull