Switch to using $() for subshells, part 1

Cleanup every use of `` for subshells in the nodepool and tools
directory , replacing them with $(), and finally making the scripts
consistent.

Change-Id: I2b05cd20f9c9a30ab88f8db235aa81da93b1fad3

nodepool/elements/puppet/pre-install.d/10-preseed

@@ -23,11 +23,11 @@
 set -e
 
 # If lsb_release is missing, just do nothing.
-DISTRO=`lsb_release -si` || true
+DISTRO=$(lsb_release -si) || true
 
 case $DISTRO in
     'Ubuntu'|'Debian')
-    PRESEED=`mktemp`
+    PRESEED=$(mktemp)
     cat > $PRESEED <<EOF
 d-i iptables-persistent/autosave_done boolean true
 d-i iptables-persistent/autosave_v4 boolean false

nodepool/scripts/install_devstack_dependencies.sh

@@ -43,7 +43,7 @@ elif [ -f /usr/bin/apt-get ]; then
         sudo DEBIAN_FRONTEND=noninteractive apt-get \
             --option "Dpkg::Options::=--force-confold" \
             --assume-yes install build-essential python-dev \
-            python-software-properties linux-headers-virtual linux-headers-`uname -r`
+            python-software-properties linux-headers-virtual linux-headers-$(uname -r)
     fi
 else
     echo "Unsupported distro."

nodepool/scripts/multinode_setup.sh

@@ -18,7 +18,7 @@
 
 export PATH=$PATH:/usr/local/sbin:/usr/sbin
 
-for ip in `cat /etc/nodepool/primary_node /etc/nodepool/sub_nodes /etc/nodepool/primary_node_private /etc/nodepool/sub_nodes_private | sort -u`; do
+for ip in $(cat /etc/nodepool/primary_node /etc/nodepool/sub_nodes /etc/nodepool/primary_node_private /etc/nodepool/sub_nodes_private | sort -u); do
     sudo iptables -I openstack-INPUT 1 -s $ip -j ACCEPT
 done
 
@@ -26,7 +26,7 @@ echo "" >> /home/jenkins/.ssh/authorized_keys
 cat /etc/nodepool/id_rsa.pub >> /home/jenkins/.ssh/authorized_keys
 echo "" >> /home/jenkins/.ssh/authorized_keys
 
-ROLE=`cat /etc/nodepool/role`
+ROLE=$(cat /etc/nodepool/role)
 if [ $ROLE == "primary" ]; then
     cp /etc/nodepool/id_rsa /home/jenkins/.ssh/id_rsa
     chmod 0600 /home/jenkins/.ssh/id_rsa

nodepool/scripts/prepare_devstack.sh

@@ -18,7 +18,7 @@
 
 cd /opt/nodepool-scripts/
 ./install_devstack_dependencies.sh
-DISTRIB_CODENAME=`lsb_release -sc`
+DISTRIB_CODENAME=$(lsb_release -sc)
 python ./cache_devstack.py $DISTRIB_CODENAME
 
 sync

tools/check_valid_gerrit_config.sh

@@ -2,7 +2,7 @@
 
 # It checks that *.config files respect certain gerrit ACL rules
 
-export TMPDIR=`/bin/mktemp -d`
+export TMPDIR=$(/bin/mktemp -d)
 trap "rm -rf $TMPDIR" EXIT
 
 pushd $TMPDIR

tools/mount-image.sh

@@ -22,7 +22,7 @@ rm -rf /tmp/newimage
 mkdir -p /tmp/newimage
 
 #qemu-nbd needs the absolute path of the image
-qemu-nbd -c /dev/nbd1 `readlink -e $IMAGE`
+qemu-nbd -c /dev/nbd1 $(readlink -e $IMAGE)
 
 #mount the first partition
 mount /dev/nbd1p1 /tmp/newimage

tools/run-compare-xml.sh

@@ -28,7 +28,7 @@ mkdir -p .test/new/config
 mkdir -p .test/new/out
 cd ../..
 
-GITHEAD=`git rev-parse HEAD`
+GITHEAD=$(git rev-parse HEAD)
 
 # First generate output from HEAD~1
 git checkout HEAD~1