Serverless Application Conditional Creation

**Description:**
It seems that Conditional attribute is not being respected for `AWS::Serverless::Application`

**Steps to reproduce the issue:**
1. Define `AWS::Serverless::Application` pointing to non-public application in us-east-2
2. Add conditional statement that evaluates to False
3. run sam build --region us-west-2

**Observed result:**
I get the following error:
`samcli.commands.validate.lib.exceptions.InvalidSamDocumentException: [InvalidResourceException('', 'Application with id arn:aws:serverlessrepo:us-east-2::applications/ could not be found.')] ('', 'Application with id arn:aws:serverlessrepo:us-east-2::applications/ could not be found.')`

**Expected result:**
The expected result would be for the application to be ignored and not built