[access] waiting for subscription can be expensive

e.g. upower can delay loading

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>
[server] pass changed signal through slot first

This allow to track signal in future for debugging purposes

Signed-off-by: Denis Zalevskiy <denis.zalevskiy@jolla.com>
Merge pull request #4 from deztructor/master

Do not wait for subscription