Implement while loop for initial fetches

[marthoc]

Simple while loop prevents the initialization from continuing unless both fetches (status and control) return successfully. This blocks the startup of Homebridge until HomeSeer is started, ensuring that HomeSeer devices will be set up in Homebridge.

Related issues/PRs: #120. #116.

Tested with HS4:

• Start Homebridge without HomeSeer started.
• Homebridge indicates an error that it cannot fetch data from HomeSeer.
• Start HomeSeer.
• Homebridge connects and completes startup.

[jvmahon]

I made the retry time a little longer -- 15 seconds instead of 5 -- but otherwise incorporated the change. Thanks.

[marthoc]

@jvmahon Thanks for merging! Just tested the published version and it works well on my setup.