Set the database.connection option default value

This was previously set right before ironic-api start, but the
default value must also be present for ironic-dbsync calls.

Note: the default value of database.connection is changed here - from
now on the sqlite database will be stored in ./ironic/ironic.sqlite
instead of ./ironic/openstack/common/db/ironic.sqlite.

Closes-Bug: #1290645

Change-Id: I2c2ab2f10a99ffd564611351e71c0b88adc20ba7
Merge "Set the database.connection option default value"