clear asterisk variables before "recog" and "synth" operations

[userator]

I propose to implement the mechanism of preliminary purification of asterisk variables in order to prevent, in an asterisk variable, the values obtained from the penultimate query, in the case when the last query was unsuccessful.

variables value:

RECOGSTATUS
RECOG_STATUS
RECOG_COMPLETION_CAUSE
RECOG_RESULT
SYNTHSTATUS

variables used in functions:

RECOG_CONFIDENCE()
RECOG_GRAMMAR()
RECOG_INPUT()
RECOG_INSTANCE()

[achaloyan]

Thanks for your suggestion. That makes sense. If you could implement the changes and provide a patch, that would help. Otherwise, I personally will not be able to take a closer look at this any soon.