[multipass] remove blockage among --both-distros option

multipass/run_parallel_iiab_test.sh

@@ -52,7 +52,7 @@ LOCAL_VARS_URL="${LOCAL_VARS_URL:-https://raw.githubusercontent.com/iiab/iiab/re
 
 WAIT_TRIES="${WAIT_TRIES:-60}"     # used ONLY for the first auto-resume
 WAIT_SLEEP="${WAIT_SLEEP:-5}"
-STAGGER="${STAGGER:-15}"
+STAGGER="${STAGGER:-20}"
 
 ACTION="run"
 modules=()
@@ -505,9 +505,7 @@ fi
 
 case "$ACTION" in
   run)
-    phase_parallel_stagger launch
-    phase_parallel_stagger install
-    phase_parallel_stagger resume 1
+    pipeline_parallel_stagger
     summary
     ;;
   continue)