use branch 0.9.7 for sipsak in debian containers

docker/Dockerfile.debian10

@@ -74,7 +74,7 @@ RUN rm -rf /var/lib/mysql && mkdir -p /var/lib/mysql /var/run/mysqld \
 RUN mysql_install_db --user=mysql
 
 WORKDIR /usr/local/src
-RUN git clone https://github.com/nils-ohlmeier/sipsak
+RUN git clone -b 0.9.7 https://github.com/nils-ohlmeier/sipsak
 WORKDIR /usr/local/src/sipsak
 RUN autoreconf --install
 RUN ./configure

docker/Dockerfile.debian9

@@ -75,7 +75,7 @@ RUN rm -rf /var/lib/mysql && mkdir -p /var/lib/mysql /var/run/mysqld \
 RUN mysql_install_db --user=mysql
 
 WORKDIR /usr/local/src
-RUN git clone https://github.com/nils-ohlmeier/sipsak
+RUN git clone -b 0.9.7 https://github.com/nils-ohlmeier/sipsak
 WORKDIR /usr/local/src/sipsak
 RUN autoreconf --install
 RUN ./configure