Metric values should be properly formatted

[avsigaev]

:~$ sonmcli worker metrics
metrics:
cpu_utilization: 77.88697787944405
disk_free: 1.93787846656e+11
disk_total: 2.31197970432e+11
gpu0_fan: 91
gpu0_power: 153
gpu0_temp: 84
gpu1_fan: 59
gpu1_power: 126
gpu1_temp: 82
ram_free: 1.3919563776e+10
ram_total: 1.6747761664e+10