Selftest failed on serial remote session when temp sensor is not detected

[prasimix]

If error selftest is initiated via serial remote session (e.g. SYST:POW 1 or *TST?) and any of channel's temp sensor is not detected (e.g. the Power board is detached or sensor is damaged) a firmware will stuck and only hard reset can help.
To reproduce it unplug one Power board from the Arduino shield, power up PSU, initiate serial session and execute *TST?

[mvladic]

Apparently, there is an limit of max. 64 characters when printing strings using Serial.println(const char *).

Following string was printed when CH2 temperature sensor test failed:

**ERROR [2017-08-29 13:03:14]: 723,"CH2 temperature sensor test failed"

which has 71 characters. That was cause of blocking.

In this fix, I replaced single println with multiple print's followed by the println at the end.

[prasimix]

Now it works but for some reason temp error is reported twice:

*TST?
**ERROR [2017-10-02 10:41:20]: 723,"CH2 temperature sensor test failed"
**ERROR [2017-10-02 10:41:20]: 723,"CH2 temperature sensor test failed"
**TRACE [2017-10-02 10:41:20]: Ch2 IO expander reg check failure: reg=0, expected=101, got=0
**ERROR [2017-10-02 10:41:20]: 211,"CH2 IOEXP test failed"
**TRACE [2017-10-02 10:41:20]: Ch2 ADC test failed reg1: expected=160, got=0
**TRACE [2017-10-02 10:41:20]: Ch2 ADC test failed reg2: expected=96, got=0
**ERROR [2017-10-02 10:41:20]: 221,"CH2 ADC test failed"
**TRACE [2017-10-02 10:41:20]: Ch2 DAC test skipped because of IO expander
**TRACE [2017-10-02 10:41:20]: Fan RPM: 3654
1

[prasimix]

Fixed