The previous commit prompted a new error:
```
2024-06-01 10:54:08,310|ERROR|platypush:plugin:bluetooth|module 'platypush.entities.time' has no attribute 'time'
Traceback (most recent call last):
File "/usr/lib/python3.9/dist-packages/platypush/plugins/__init__.py", line 247, in _runner
self.main()
File "/usr/lib/python3.9/dist-packages/platypush/plugins/bluetooth/__init__.py", line 590, in main
self._refresh_cache()
File "/usr/lib/python3.9/dist-packages/platypush/plugins/bluetooth/__init__.py", line 146, in _refresh_cache
get_entities_engine().wait_start()
File "/usr/lib/python3.9/dist-packages/platypush/entities/__init__.py", line 48, in get_entities_engine
time_start = time.time()
AttributeError: module 'platypush.entities.time' has no attribute 'time'
```
Which explains even the previous error: `import time` in that module
won't use the `time` module from the Python library, but the `.time`
module within the same directory.
This error only happens when the current directory is part of PYTHONPATH
(and usually it shouldn't), but for sake of keeping things safe I've
replaced `time()` with `utcnow().timestamp()`, with `utcnow` imported
from `platypush.utils`.