RUM-9899: fix sampling rate logic

Author: satween

dd-sdk-android-internal/api/apiSurface

@@ -74,6 +74,7 @@ data class com.datadog.android.internal.telemetry.TracingHeaderTypesSet
 class com.datadog.android.internal.thread.NamedRunnable : Runnable
   constructor(String, Runnable)
 fun ByteArray.toHexString(): String
+fun <R> Any.tryCastTo(): R?
 object com.datadog.android.internal.utils.ImageViewUtils
   fun resolveParentRectAbsPosition(android.view.View, Boolean = true): android.graphics.Rect
   fun calculateClipping(android.graphics.Rect, android.graphics.Rect, Float): android.graphics.Rect

integrations/dd-sdk-android-okhttp/src/main/kotlin/com/datadog/android/okhttp/trace/TracingInterceptor.kt

@@ -219,7 +219,7 @@ internal constructor(
         if (span is DDSpan && span.isRootSpan) {
             val samplingPriority = if (isSampled) PrioritySampling.SAMPLER_KEEP else PrioritySampling.SAMPLER_DROP
             val spanContext = span.context()
-            if (spanContext.setSamplingPriority(samplingPriority, SamplingMechanism.EXTERNAL_OVERRIDE.toInt())) {
+            if (spanContext.setSamplingPriority(samplingPriority, SamplingMechanism.DEFAULT.toInt())) {
                 spanContext.setMetric(
                     AGENT_PSR_ATTRIBUTE,
                     (traceSampler.getSampleRate() ?: ZERO_SAMPLE_RATE) / ALL_IN_SAMPLE_RATE