Patch for preventing multiple installations/uninstallation at a same time

Signed-off-by: Arpit Goyal <agmps17@gmail.com>
Using ensure block to release lock
Using transaction to avoid race conditions

Signed-off-by: Arpit Goyal <agmps17@gmail.com>
removing aux variables

Signed-off-by: Arpit Goyal <agmps17@gmail.com>
Merge branch 'simultaneous-app-install' of https://github.com/agmps17/platform into simultaneous-app-install
Merge pull request #92 from agmps17/simultaneous-app-install

Simultaneous app install