"Autoupdate" actually drops tables instead of altering them

[ricky92]

I tried digging into the source code and found the cause to this issue:
https://github.com/strongloop/loopback-datasource-juggler/blob/6b83b6f4d1a4941917ffbaf8cebf476e40a53f83/lib/datasource.js#L1141

Apparently, the autoupdate function waits for the connection to be established before proceeding with its execution, but instead of queuing itself it queues the automigrate function. This causes tables to be dropped instead of altered.

[dhmlau]

@ricky92, would you be interested in submitting a patch? Thanks.