Improve node verifier output

[pepoviola]

Currently we verify if all the nodes in the network are up by querying the /metrics endpoint. (to get the process start time). This process is reusing internal logic of the metrics module, but is not great to display the temp. errors to users like we are doing now

Error 	 fetching metrics from: http://127.0.0.1:40327/metrics

Error 	 fetching metrics from: http://127.0.0.1:36243/metrics

Error 	 fetching metrics from: http://127.0.0.1:35915/metrics

Error 	 fetching metrics from: http://127.0.0.1:42557/metrics

Error 	 fetching metrics from: http://127.0.0.1:42479/metrics

As we know that the init process of the nodes can take some time (at least to start to response from the prometheus server) we should improve the way we display this to users, since this are know and expected errors we can just have some progress bar or something similar.