Allow to set log file name + minor bug fix

[christian-bromann]

Hey,
this patch contains following patches:

• fix usage of multiremote, which have capabilities set as follows:

  capabilities: {
        myChromeBrowser: {
            port: 4446,
            capabilities: {
                browserName: 'chrome',
                acceptInsecureCerts: true
            }
        },
        myFFBrowser: {
            port: 4445,
            capabilities: {
                browserName: 'firefox',
                acceptInsecureCerts: true
            }
        }
    },

• add option to allow setting custom log file name because why not 🤷‍♂️

• rename default log file name for chromedriver to wdio-chromedriver.log to align with the other wdio specific log files.

Cheers

[atti187]

Released as 6.0.4. Cheers!