set the env vars only if the are not alredy set (do not overwrite existing values)

Author: lucaspimentel

scripts/datadog_wrapper

@@ -81,16 +81,16 @@ then
   fi
 
   # Required environment variables for .NET library
-  export CORECLR_ENABLE_PROFILING="1"
-  export CORECLR_PROFILER="{846F5F1C-F9AE-4B07-969E-05C26BC060D8}"
-  export DD_DOTNET_TRACER_HOME="/opt/datadog"
+  export CORECLR_ENABLE_PROFILING="${CORECLR_ENABLE_PROFILING:-"1"}"
+  export CORECLR_PROFILER="${CORECLR_PROFILER:-"{846F5F1C-F9AE-4B07-969E-05C26BC060D8}"}"
+  export DD_DOTNET_TRACER_HOME="${DD_DOTNET_TRACER_HOME:-"/opt/datadog"}"
 
   # Disabled .NET library features
-  export DD_TRACE_STARTUP_LOGS=0
-  export DD_INSTRUMENTATION_TELEMETRY_ENABLED="${DD_INSTRUMENTATION_TELEMETRY_ENABLED:-false}" # disable telemetry, unless it was already enabled above
-  export DD_CIVISIBILITY_ENABLED=0 # disable CI Visibility's auto-detect mechanism
-  export DD_APPSEC_ENABLED=0 # not supported in Lambda yet
-  export DD_PROFILING_ENABLED=0 # not supported in Lambda yet
+  export DD_TRACE_STARTUP_LOGS="${DD_TRACE_STARTUP_LOGS:-"0"}"
+  export DD_INSTRUMENTATION_TELEMETRY_ENABLED="${DD_INSTRUMENTATION_TELEMETRY_ENABLED:-"0"}" # disable telemetry, unless it was already enabled above
+  export DD_CIVISIBILITY_ENABLED="${DD_CIVISIBILITY_ENABLED:-"0"}"                           # disable CI Visibility's auto-detect mechanism
+  export DD_APPSEC_ENABLED="${DD_APPSEC_ENABLED:-"0"}"                                       # not supported in Lambda yet
+  export DD_PROFILING_ENABLED="${DD_PROFILING_ENABLED:-"0"}"                                 # not supported in Lambda yet
 fi # .NET
 
 # if it is java