StackExchangeRedis2PlusWrapper can create multiple SessionCache instances

[tippmar-nr]

Description
Recent customer-supplied memory dumps have revealed that the agent is holding 2 instances of SessionCache when we only intend for there to be a single instance. This would appear to be a race condition when StackExchange.Redis.ConnectionMultiplexer.CreateMultiplexer is called multiple times in quick succession, or it may be related to an agent restart.

In any case, we should consider adding some locking in the RegisterProfiler() callback in ConnectWrapperV2.cs

Expected Behavior
The agent should use a single instance of the SessionCache

For Maintainers Only or Hero Triaging this bug
Suggested Priority (P1,P2,P3,P4,P5):
P3
Suggested T-Shirt size (S, M, L, XL, Unknown):
S

[workato-integration]

https://new-relic.atlassian.net/browse/NR-213768