nmet dependencies when docker build for zoneminder ubuntu18.04

[matthewgan]

When creating an issue, please provide the following information:

• /Release/Ubuntu18.04/Dockerfile

Error log:

The following packages have unmet dependencies:
 zoneminder : Depends: libswscale5 but it is not installable
              Depends: libswresample3 but it is not installable
              Recommends: apache2 (>= 2.4.6-4~) but it is not going to be installed or
                          nginx or
                          httpd
              Recommends: libapache2-mod-php or
                          php-fpm
              Recommends: default-mysql-server but it is not going to be installed or
                          mariadb-server but it is not going to be installed or
                          virtual-mysql-server
              Recommends: zoneminder-doc (>= 1.36.15-bionic1) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.
The command '/bin/sh -c DEBIAN_FRONTEND=noninteractive apt install --assume-yes zoneminder     && a2enconf zoneminder     && a2enmod rewrite cgi' returned a non-zero code: 100