Waggle Dance fails to serve when destination bastion is down/unreachable

[pradeepbhadani]

Issue:
Waggle Dance federates to primary Metasotre A and foreign Metastore B (over SSH Tunnel through bastion host BH).
If for any reason, BH is down/unreachable or disallow SSH connection then this cause whole WD to stops serving request even for Metastore A.

Excepted Behaviour:
WD to handle the above situation gracefully and continue to serve rest of the Metastores.

Current Behaviour:
WD fails to serve all requests.

[patduin]

Slightly related to #73 (that fixed the connection issue "after" the tunnel). Something similar is happening when the actual tunnel is failing to connect, WD doesn't handle it well. Looking into it...