MongoDB - Fix write_concern param

[Zlaticanin]

When Vault deletes a user on a MongoDB replica, it always uses WriteConcern = 'majority' despite the setting in the connection configuration.

Results from the log without the fix using write_concern="{\"W\": 1}":

{"t":{"$date":"2022-12-21T23:58:20.295+00:00"},"s":"I",  "c":"COMMAND",  "id":51803,   "ctx":"conn52","msg":"Slow query","attr":{"type":"command","ns":"admin.$cmd","appName":"mongosh 1.6.1","command":{"dropUser":"v-token-XXXXX-XXXXXXXXXXX-XXXXXX","writeConcern":{"w":"majority"},"lsid":{"id":{"$uuid":"503728f4-f4a7-45bc-bee5-cd9f36bf831b"}},"$clusterTime":{"clusterTime":{"$timestamp":{"t":1671667098,"i":1}},"signature":{"hash":{"$binary":{"base64":"AAAAAAAAAAAAAAAAAAAAAAAAAAA=","subType":"0"}},"keyId":0}},"$db":"admin","$readPreference":{"mode":"primaryPreferred"}},"numYields":0,"reslen":163,"locks":{"ParallelBatchWriterMode":{"acquireCount":{"r":2}},"FeatureCompatibilityVersion":{"acquireCount":{"r":3,"w":2}},"ReplicationStateTransition":{"acquireCount":{"w":5}},"Global":{"acquireCount":{"r":3,"w":2}},"Database":{"acquireCount":{"w":2}},"Collection":{"acquireCount":{"w":2}},"Mutex":{"acquireCount":{"r":2}}},"flowControl":{"acquireCount":2,"timeAcquiringMicros":1},"writeConcern":{"w":"majority","wtimeout":0,"provenance":"clientSupplied"},"storage":{},"remote":"172.24.0.1:62688","protocol":"op_msg","durationMillis":5}}

Results from the log with the fix using write_concern="{\"W\": 1}":

{"t":{"$date":"2022-12-23T21:26:35.031+00:00"},"s":"I",  "c":"COMMAND",  "id":51803,   "ctx":"conn76","msg":"Slow query","attr":{"type":"command","ns":"admin.$cmd","appName":"mongosh 1.6.1","command":{"dropUser":"v-token-my-role-XXXXX-XXXXXXXXXXX-XXXXXX","writeConcern":{"w":1},"lsid":{"id":{"$uuid":"07037c7b-6701-4cbb-8547-4ee40ba97542"}},"$clusterTime":{"clusterTime":{"$timestamp":{"t":1671830794,"i":1}},"signature":{"hash":{"$binary":{"base64":"AAAAAAAAAAAAAAAAAAAAAAAAAAA=","subType":"0"}},"keyId":0}},"$db":"admin","$readPreference":{"mode":"primaryPreferred"}},"numYields":0,"reslen":163,"locks":{"ParallelBatchWriterMode":{"acquireCount":{"r":2}},"FeatureCompatibilityVersion":{"acquireCount":{"r":3,"w":2}},"ReplicationStateTransition":{"acquireCount":{"w":5}},"Global":{"acquireCount":{"r":3,"w":2}},"Database":{"acquireCount":{"w":2}},"Collection":{"acquireCount":{"w":2}},"Mutex":{"acquireCount":{"r":2}}},"flowControl":{"acquireCount":2,"timeAcquiringMicros":1},"writeConcern":{"w":1,"wtimeout":0,"provenance":"clientSupplied"},"storage":{},"remote":"172.20.0.1:56816","protocol":"op_msg","durationMillis":1}}

[swenson]

LGTM

[austingebauer]

We should backport this as well. Thanks, @MilenaHC 👍