Detects nginx-extras package. Fixes #3891.

debian/control

 
 Package: jitsi-meet-web-config
 Architecture: all
-Depends: openssl, openjdk-8-jre-headless | nginx | apache2
+Depends: openssl, openjdk-8-jre-headless | nginx | nginx-extras | apache2
 Description: Configuration for web serving of Jitsi Meet
  Jitsi Meet is a WebRTC JavaScript application that uses Jitsi
  Videobridge to provide high quality, scalable video conferences.

debian/jitsi-meet-web-config.postinst

         db_set jitsi-meet/jvb-hostname $JVB_HOSTNAME
 
         NGINX_INSTALL_CHECK="$(dpkg-query -f '${Status}' -W 'nginx' 2>/dev/null | awk '{print $3}' || true)"
-        if [ "$NGINX_INSTALL_CHECK" = "installed" ] || [ "$NGINX_INSTALL_CHECK" = "unpacked" ] ; then
+        NGINX_EXTRAS_INSTALL_CHECK="$(dpkg-query -f '${Status}' -W 'nginx-extras' 2>/dev/null | awk '{print $3}' || true)"
+        if [ "$NGINX_INSTALL_CHECK" = "installed" ] \
+           || [ "$NGINX_INSTALL_CHECK" = "unpacked" ] \
+           || [ "$NGINX_EXTRAS_INSTALL_CHECK" = "installed" ] \
+           || [ "$NGINX_EXTRAS_INSTALL_CHECK" = "unpacked" ] ; then
             FORCE_NGINX="true"
         fi
         APACHE_INSTALL_CHECK="$(dpkg-query -f '${Status}' -W 'apache2' 2>/dev/null | awk '{print $3}' || true)"