decproxy2: cleanup debug log and state change code
decproxy2: cleanup debug log and state change code

Change-Id: Ie702464458546572e86d1eb14a158189b4d72c7f
Reviewed-on: https://gpro.lgsvl.com/77698
Reviewed-by: Wonchul Lee <9841bdbec9dbb2acc2dcaaa1dab0491399f0e464@lge.com>
Tested-by: Wonchul Lee <9841bdbec9dbb2acc2dcaaa1dab0491399f0e464@lge.com>

justinjoy/gst-plugins-cool,justinjoy/gst-plugins-cool