CLOUDSTACK-6212: Let vm_instance table's ID field be unique and auto_increment

`vm_instance` table's id column is unique but does not auto_increment like other
resource tables. The fix simply alter the table's id column to have it
auto_increment which may avoid id conflicts in a multi-master mysql setup.

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>
CLOUDSTACK-6212: auto_increment for some other resource tables

This fix alters table columns which are primary keys but don't have them
auto_increment such as region, domain_router, user_vm etc.

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>
Merge branch 'hotfix/CLOUDSTACK-6212' into 4.5

This closes #52

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>