feat(Cloud Databases): Allow users to edit configuration on database creation

[omaraibrahim]

Users cannot edit their database configuration on database creation. This PR allows users to do so.

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Relates OR Closes #0000

Output from acceptance testing:

$ make testacc TEST=./ibm/service/database TESTARGS='-run=TestAccIBMDatabaseInstancePostgresBasic'
--- PASS: TestAccIBMDatabaseInstancePostgresBasic
PASS
ok  	github.com/IBM-Cloud/terraform-provider-ibm/ibm/service/database

$  make testacc TEST=./ibm/service/database TESTARGS='-run=TestAccIBMDatabaseInstanceMongodbBasic'
--- PASS: TestAccIBMDatabaseInstanceMongodbBasic (1138.88s)
PASS
ok      github.com/IBM-Cloud/terraform-provider-ibm/ibm/service/database        1139.922s

make testacc TEST=./ibm/service/database TESTARGS='-run=TestAccIBMDatabaseInstance_Redis_Basic'
--- PASS: TestAccIBMDatabaseInstance_Redis_Basic (790.05s)
PASS
ok      github.com/IBM-Cloud/terraform-provider-ibm/ibm/service/database        791.109s