RENG-145 Update config.sh fetch and pass upstream branch to the linux-pkg ant task

PR URL: https://www.github.com/delphix/linux-pkg/pull/296

Author: shishaktdlpx

packages/virtualization/config.sh

@@ -66,6 +66,8 @@ function build() {
 	# 'nothing' if 'variable' is not set. Because 'nothing' is not defined it evaluates to "" when 'variable'
 	# is not set. So [[ "" ]] is what is actually evaluated when 'variable' is not set.
 
+	args+=("-Dbuild.branch=$DEFAULT_GIT_BRANCH")
+
 	if [[ ${SECRET_DB_USE_JUMPBOX+nothing} ]]; then
 		args+=("-DSECRET_DB_USE_JUMPBOX=$SECRET_DB_USE_JUMPBOX")
 	fi