Don't start pollers when tracing is disabled

[yogiraj07]

Background

2 pollers are started in the background for DefaultSamplingStrategy

1. When the first incoming request for the framework arrives : code
2. BeginSegment() makes a sampling decision : code

Issue

When tracing is disabled using X-Ray SDK Configuration or by creating custom recorder instance, the pollers are still started. Reference : #80

Expected Behavior

Pollers should not be started when tracing is disabled,

Usecase

1. For unit testing, user can disable tracing.
2. For various stages such dev , alpha, beta customers may not want to enable X-Ray and not launch the X-Ray daemon. In the current scenario, pollers are unnecessary started leading to using resources.

Solution

Add IsTracingDisabled() check in the ShouldTrace() before starting poller.

[srprash]

Fixed in v2.7.0
Please refer to the Changelog