More stability fixes around "set" (and "get")

[Apollon77]

This PR includes:

• adding more guards to ensure we only throw or reject once in set()
• Make sure "set()" throws in timeout cases also to prevent "get via set" to return undefined in an unexpected way
• moves a set-in-progress guard to the right place
• adds catches for "get/refresh data on connect" to not crash uncatcheable

[coveralls]

coverage: 58.291% (-0.6%) from 58.841%
when pulling 960babe on set-fixes
into 4f488ed on master.