Various improvements to p4vm scripts

- Allow running up to a given step of install-p4-tools.sh
(e.g. helpful to install only PI)
- Install fabric-p4test deps (ONOS-7656)
- Fix python protobuf libraries not installed

Change-Id: I443edb08f455703ae682e485a89d793a584c30ff
diff --git a/tools/dev/p4vm/root-bootstrap.sh b/tools/dev/p4vm/root-bootstrap.sh
index f413cc6..7b28487 100755
--- a/tools/dev/p4vm/root-bootstrap.sh
+++ b/tools/dev/p4vm/root-bootstrap.sh
@@ -24,8 +24,10 @@
 apt-get install software-properties-common -y
 add-apt-repository ppa:webupd8team/java -y
 apt-get update
-echo "oracle-java8-installer shared/accepted-oracle-license-v1-1 select true" | debconf-set-selections
 
+DEBIAN_FRONTEND=noninteractive apt-get -y -o Dpkg::Options::="--force-confdef" -o Dpkg::Options::="--force-confold" upgrade
+
+echo "oracle-java8-installer shared/accepted-oracle-license-v1-1 select true" | debconf-set-selections
 apt-get -y --no-install-recommends install \
     avahi-daemon \
     bridge-utils \