Add a threshold for expected zero values in the SPM script (#5753)

## Which problem is this PR solving?
- Makes sure the SPM CI doesn't fail if the first value received is
zero.

## Description of the changes
- The script now waits until the threshold (Currently set to 3) number
of zero values are received before throwing an error

## How was this change tested?
- Manually

## Checklist
- [x] I have read
https://github.com/jaegertracing/jaeger/blob/master/CONTRIBUTING_GUIDELINES.md
- [x] I have signed all commits
- [ ] I have added unit tests for the new functionality
- [ ] I have run lint and test steps successfully
  - for `jaeger`: `make lint test`
  - for `jaeger-ui`: `yarn lint` and `yarn test`

---------

Signed-off-by: FlamingSaint <[email protected]>

scripts/spm-integration-test.sh

@@ -61,17 +61,24 @@ validate_service_metrics() {
     # Store the values in an array
     mapfile -t metric_points < <(echo "$response" | jq -r '.metrics[0].metricPoints[].gaugeValue.doubleValue')
     echo "Metric datapoints found for service '$service': " "${metric_points[@]}"
-    # Check that all values are non-zero
+    # Check that atleast some values are non-zero after the threshold
     local non_zero_count=0
+    local expected_non_zero_count=3
+    local zero_count=0
+    local expected_max_zero_count=3
     for value in "${metric_points[@]}"; do
       if [[ $(echo "$value > 0.0" | bc) == "1" ]]; then
         non_zero_count=$((non_zero_count + 1))
       else
-        echo "❌ ERROR: Zero values not expected"
+        zero_count=$((zero_count + 1))
+      fi
+
+      if [[ $zero_count -gt $expected_max_zero_count ]]; then
+        echo "❌ ERROR: Zero values crossing threshold limit not expected (Threshold limit - '$expected_max_zero_count')"
         return 1
       fi
     done
-    if [ $non_zero_count -lt 3 ]; then
+    if [ $non_zero_count -lt $expected_non_zero_count ]; then
       echo "⏳ Expecting at least 3 non-zero data points"
       return 1
     fi