[ale] Improve handling of unusual error reports.

Previously it was assumed if the first item in the report is tuple,
then the entire report consists only of the tuples. But this is not
true for example for the reports that are produced by mochiweb:

  error_logger:error_report(
    [{application, mochiweb},
     "Accept failed error",
     lists:flatten(io_lib:format("~p", [Other]))])

The output for such a report will looks like this:

=========================ERROR REPORT=========================
         application: mochiweb
                      "Accept failed error"
                      "{error,{tls_alert,\"unknown ca\"}}"

Change-Id: I4e0c4008806b7f039747d74178a49fd71ab352ce
Reviewed-on: http://review.couchbase.org/37966
Tested-by: Aliaksey Artamonau <aliaksiej.artamonau@gmail.com>
Reviewed-by: Aliaksey Kandratsenka <alkondratenko@gmail.com>