Use external pre-baked docker image for fedora tests to speed them up

.travis.yml

@@ -5,7 +5,7 @@ script:
     - ./test 
 
 env:
-    - DETECTED_OS=fedora:24
+    - DETECTED_OS=fedora:24 DOCKER_IMAGE=cyplo/fedora24_base NO_COMPILE_VIM=true
     - DETECTED_OS=debian:jessie NOUPGRADE=true
     - DETECTED_OS=ubuntu:trusty
     - DETECTED_OS=ubuntu:xenial

fedora/configure_fresh_system

@@ -25,21 +25,23 @@ if [[ -z $NO_SYSTEMCTL ]]; then
     sudo systemctl list-timers "*dnf-*"
 fi
 
-VIM_BUILD_DIR=/tmp
-cd "$VIM_BUILD_DIR"
-git clone https://github.com/vim/vim.git
-cd vim
-./configure --with-features=huge \
+if [[ -z $NO_COMPILE_VIM ]]; then
+    VIM_BUILD_DIR=/tmp
+    cd "$VIM_BUILD_DIR"
+    git clone https://github.com/vim/vim.git
+    cd vim
+    ./configure --with-features=huge \
                 --enable-multibyte \
                 --enable-rubyinterp \
                 --enable-python3interp=yes \
                 --enable-luainterp \
                 --enable-gui=no \
                 --enable-cscope 
-make -j2
-sudo make install
-cd
-rm -fvr "$VIM_BUILD_DIR/vim"
+    make -j2
+    sudo make install
+    cd
+    rm -fvr "$VIM_BUILD_DIR/vim"
+fi
 
 DIR="$DIR/../"
 DIR="$DIR" $DIR/common/configure_fresh_system

test

@@ -25,5 +25,9 @@ else
     DIR=$SYSTEM_DIR
 fi
 
-docker run -v $CURRENT_DIR:$INSIDER_ROOT_DIR $DETECTED_OS $INSIDER_ROOT_DIR/$DIR/test_insider
+if [[ -z $DOCKER_IMAGE ]]; then
+    DOCKER_IMAGE="$DETECTED_OS"
+fi
+
+docker run -v $CURRENT_DIR:$INSIDER_ROOT_DIR $DOCKER_IMAGE $INSIDER_ROOT_DIR/$DIR/test_insider