One of the first unit tests in the cli tests called the Run method.
Since the Run method called os.Exit, it reported the unit tests as
succeeded. When parallel is set to 1, this skips _all_ unit tests after
the first one. When parallel is set to a higher value, unit tests run by
other processes still get run.
This changes the Run method to return an error (if one occurred). This
error can then be printed out and a bad exit status can be used to exit
the program from the main program instead. That causes the unit tests
to run correctly regardless of how many parallel processes are running.
Also added an additional option to the CLI called `IgnoreSignals`. If
this is set to true, then signals are not registered with the process.
Setting signals doesn't really work in unit tests so it's good to ensure
they don't get set in the first place.
In addition to fixing the influx cli tests, this adds a mock client to
the cli test for Use. PR #5183 added a validation for `use` to only be
able to select public databases so `_internal` couldn't be chosen. To
implement this, the `SHOW DATABASES` command was used by the internal
client.
Some of the unit tests in `cli_test.go` don't set the client to
anything. `TestParseCommand_Use` previously didn't, but now it needs to
have a client in the unit test with an empty test server.