Use 'vm' stackwalker as default for java profiler

Author: jbachorik

dd-trace-api/src/main/java/datadog/trace/api/config/ProfilingConfig.java

@@ -138,7 +138,7 @@ public final class ProfilingConfig {
   public static final String PROFILING_DATADOG_PROFILER_LOG_LEVEL_DEFAULT = "NONE";
   public static final String PROFILING_DATADOG_PROFILER_STACKDEPTH = "profiling.ddprof.stackdepth";
   public static final String PROFILING_DATADOG_PROFILER_CSTACK = "profiling.ddprof.cstack";
-  public static final String PROFILING_DATADOG_PROFILER_CSTACK_DEFAULT = "fp";
+  public static final String PROFILING_DATADOG_PROFILER_CSTACK_DEFAULT = "vm";
   public static final String PROFILING_DATADOG_PROFILER_SAFEMODE = "profiling.ddprof.safemode";
 
   private static final int POP_METHOD = 4;