Remove unencrypted git protocol use (mininet#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