Uninitialized Variables Pass to Functions / static analysis cleanup

[brandt-nasa]

Static analyzer reports uninitialized variable warnings for variables passed to OSAL/CFE functions, even though the real implementations properly initialize ouputs.

While not a runtime bug, initializing these variables:

1. Eliminates false positive static analysis warnings
2. Follows defensive programming practices
3. Makes code more maintainable
4. Self-documents expected initial state

Locations:

• CFE_TBL_TxnOpenTableDumpFile: FileDescriptor
• CFE_SB_ReceiveTxn_PipeHandler: BufDscPtr
• CFE_TBL_WriteSnapshotToFile: FileDescriptor
• TestCDSName: IdByName
• TestCounterIDToIndex: CounterIdx
• TestAppIDToIndex: TestAppIdx
• TestPipeName: PipeNameBuf