MySQL setting remote root password + typo

1. Remote root user accessing the DB during front and batch servers installation. Password for root@% should be set. And removed afterwards.
2. Typo in 'mysql_secure_installation` description.
added missing unzip dep for the sanity tests.
an even more detailed explanation for the MySQL setup, following vadimtar's contribution.
su kaltura -c "touch $MOUNT_DIR/content creates conflict with content/ directory

Several packages create content directory. The installation fails, because content file already exists from the touch command.
Merge pull request #113 from vadimtar/patch-2

su kaltura -c "touch $MOUNT_DIR/content creates conflict with content/ d...
prep work.
Merge branch 'master' of https://github.com/kaltura/platform-install-packages
Added comment regarding desktop edition conflicts and a change in the mysql installation procedure