Add verbose logging via KASMVNC_VERBOSE_LOGGING env var

Running "KASMVNC_VERBOSE_LOGGING=1 builder/test-deb debian buster" will
turn on verbose logging of kasmvncserver.

builder/startup/vnc_startup.sh

@@ -87,9 +87,10 @@ vncserver -kill $DISPLAY &> $HOME/.vnc/vnc_startup.log \
 
 detect_www_dir
 detect_cert_location
+[ -n "$KASMVNC_VERBOSE_LOGGING" ] && verbose_logging_option="-log *:stderr:100"
 
 echo -e "start vncserver with param: VNC_COL_DEPTH=$VNC_COL_DEPTH, VNC_RESOLUTION=$VNC_RESOLUTION\n..."
-vncserver $DISPLAY -depth $VNC_COL_DEPTH -geometry $VNC_RESOLUTION -FrameRate=$MAX_FRAME_RATE -websocketPort $VNC_PORT $cert_option -sslOnly -interface 0.0.0.0 $VNCOPTIONS $package_www_dir_option #-log *:stderr:100 #&> $STARTUPDIR/no_vnc_startup.log
+vncserver $DISPLAY -depth $VNC_COL_DEPTH -geometry $VNC_RESOLUTION -FrameRate=$MAX_FRAME_RATE -websocketPort $VNC_PORT $cert_option -sslOnly -interface 0.0.0.0 $VNCOPTIONS $package_www_dir_option $verbose_logging_option #&> $STARTUPDIR/no_vnc_startup.log
 
 PID_SUN=$!
 

builder/test-deb

@@ -8,5 +8,7 @@ cd "$(dirname "$0")"
 docker build --build-arg KASMVNC_PACKAGE_DIR="build/${os_codename}" \
   -t kasmvnctester_${os}:$os_codename \
   -f dockerfile.${os}_${os_codename}.deb.test .
-docker run -it -p 443:8443 --rm -e "VNC_USER=foo" -e "VNC_PW=foobar" \
+docker run -it -p 443:8443 --rm \
+  -e KASMVNC_VERBOSE_LOGGING=$KASMVNC_VERBOSE_LOGGING \
+  -e "VNC_USER=foo" -e "VNC_PW=foobar" \
   kasmvnctester_${os}:$os_codename

builder/test-rpm

@@ -10,5 +10,8 @@ docker build --build-arg \
   KASMVNC_PACKAGE_DIR="build/${os}_${os_codename}" \
   -t kasmvnctester_${os}:$os_codename \
   -f dockerfile.${os}_${os_codename}.rpm.test .
-echo docker run -it -p 443:8443 --rm -e "VNC_USER=foo" -e "VNC_PW=foobar" \
+
+docker run -it -p 443:8443 --rm \
+  -e KASMVNC_VERBOSE_LOGGING=$KASMVNC_VERBOSE_LOGGING \
+  -e "VNC_USER=foo" -e "VNC_PW=foobar" \
   kasmvnctester_${os}:$os_codename