Pin redis extension versions

php-unit-test/7.2/Dockerfile

@@ -14,7 +14,7 @@ LABEL org.label-schema.build-date=$BUILD_DATE \
 
 RUN apk add --no-cache bash nodejs nodejs-npm $PHPIZE_DEPS \
     && pecl channel-update pecl.php.net \
-    && pecl install xdebug-3.1.6 redis \
+    && pecl install xdebug-3.1.6 redis-6.0.2 \
     && docker-php-ext-enable xdebug redis \
     && apk del --no-cache $PHPIZE_DEPS
 RUN curl -o /usr/local/bin/composer https://getcomposer.org/composer.phar \

php-unit-test/7.3/Dockerfile

@@ -15,7 +15,7 @@ LABEL org.label-schema.build-date=$BUILD_DATE \
 RUN export BUILD_DEPS="bzip2-dev icu-dev libpng-dev libzip-dev openldap-dev" \
     && apk add --no-cache bash nodejs npm $PHPIZE_DEPS $BUILD_DEPS \
     && pecl channel-update pecl.php.net \
-    && pecl install xdebug-3.1.6 redis \
+    && pecl install xdebug-3.1.6 redis-6.0.2 \
     && docker-php-ext-install bz2 gd intl ldap mysqli pdo_mysql zip \
     && docker-php-ext-enable xdebug redis \
     && apk del --no-cache $PHPIZE_DEPS