Remove unencrypted git protocol use (#1100)

Because Github removes support for unencrypted git protocol in March 2022, URLs in scripts are changed to use https.

See https://github.blog/2021-09-01-improving-git-protocol-security-github/ for details

INSTALL

@@ -51,7 +51,7 @@ like to contribute an installation script, we would welcome it!)
    If you're reading this, you've probably already done so, but the
    command to download the Mininet source code is:
 
-        git clone git://github.com/mininet/mininet.git
+        git clone https://github.com/mininet/mininet.git
 
    Note that the above git command will check out the latest and greatest
    Mininet (which we recommend!) If you want to run the last
@@ -147,7 +147,7 @@ like to contribute an installation script, we would welcome it!)
 
     * clone the Mininet repository
 
-        git clone git://github.com/mininet/mininet.git
+        git clone https://github.com/mininet/mininet.git
 
     * install Mininet, the OpenFlow reference implementation, and
       Open vSwitch

util/install.sh

@@ -231,7 +231,7 @@ function of {
     fi
     # was: git clone git://openflowswitch.org/openflow.git
     # Use our own fork on github for now:
-    git clone git://github.com/mininet/openflow
+    git clone https://github.com/mininet/openflow
     cd $BUILD_DIR/openflow
 
     # Patch controller to handle more than 16 switches
@@ -498,7 +498,7 @@ function ivs {
 
     # Install IVS from source
     cd $BUILD_DIR
-    git clone git://github.com/floodlight/ivs $IVS_SRC
+    git clone https://github.com/floodlight/ivs $IVS_SRC
     cd $IVS_SRC
     git submodule update --init
     make
@@ -518,7 +518,7 @@ function ryu {
 
     # fetch RYU
     cd $BUILD_DIR/
-    git clone git://github.com/osrg/ryu.git ryu
+    git clone https://github.com/osrg/ryu.git ryu
     cd ryu
 
     # install ryu
@@ -629,7 +629,7 @@ function oftest {
 
     # Install oftest:
     cd $BUILD_DIR/
-    git clone git://github.com/floodlight/oftest
+    git clone https://github.com/floodlight/oftest
 }
 
 # Install cbench
@@ -646,7 +646,7 @@ function cbench {
     cd $BUILD_DIR/
     # was:  git clone git://gitosis.stanford.edu/oflops.git
     # Use our own fork on github for now:
-    git clone git://github.com/mininet/oflops
+    git clone https://github.com/mininet/oflops
     cd oflops
     sh boot.sh || true # possible error in autoreconf, so run twice
     sh boot.sh

util/vm/install-mininet-vm.sh

@@ -25,7 +25,7 @@ if [ -e /etc/rc.local.backup ]; then
 fi
 # Fetch Mininet
 sudo apt-get -y -qq install git-core openssh-server
-git clone git://github.com/mininet/mininet
+git clone https://github.com/mininet/mininet
 # Optionally check out branch
 if [ "$1" != "" ]; then
     pushd mininet