Recurring exceptions and other bugs in [IconCheckPoller]

Components.Lcd.IconCheckPoller.JobTask() can cause recurring exceptions. The direct cause is that LinkState can be set to integer 0, and it is then indexed on:

LinkState = LinkState[:1]

LinkState is also being calculated incorrectly, because it is initially read as a newline-terminated string from a /sys/class file, but it is then compared to a string without newline termination without it first being stripped of trailing whitespace. These errors can result in LinkState being forced to 0 when it should not be.

If /sys/class/net/eth0/operstate is read and contains "down" (and is compared correctly), then the link state value written to /proc/stb/lcd/symbol_network will be 'd', rather than '0' or '1' as intended.

If a WLAN device is present, but not configured, but the Ethernet connection is up and running, the LinkStatus will be reported only for the WLAN device. The link should be shown as up if either WLAN or Ethernet is up. In the current code, this will also force LinkStatus to be set to integer 0 and cause the exception.

For flexibility, the code should probably enumerate the attached network devices. There's existing code to do that.

Extract from debug log:

Unhandled error in Deferred:
Unhandled Error
Traceback (most recent call last):
  File "/usr/lib/python2.7/threading.py", line 524, in __bootstrap

  File "/usr/lib/python2.7/threading.py", line 551, in __bootstrap_inner

  File "/usr/lib/python2.7/threading.py", line 504, in run

--- <exception caught here> ---
  File "/usr/lib/python2.7/site-packages/twisted/python/threadpool.py", line 19
1, in _worker
    result = context.call(ctx, function, *args, **kwargs)
  File "/usr/lib/python2.7/site-packages/twisted/python/context.py", line 118, 
in callWithContext
    return self.currentContext().callWithContext(ctx, func, *args, **kw)
  File "/usr/lib/python2.7/site-packages/twisted/python/context.py", line 81, i
n callWithContext
    return func(*args,**kw)
  File "/usr/lib/enigma2/python/Components/Lcd.py", line 60, in JobTask

exceptions.TypeError: 'int' object has no attribute '__getitem__'

Reproduction steps

Enable debug logging on the T3 using Open Webif if it is not enabled.

Attach a USB WLAN dongle, but do not configure it. This will force LinkStatus to be set to integer 0.

Wait at least 30 seconds for the icon check to run.

Examine the debug log. Searching for the string "Components/Lcd.py" should find the exceptions being generated.

I've set Reproducability to Always, because these conditions should always trigger the exception.

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