sunrpc: remove redundant initialization of sock

sock is being initialized and then being almost immediately updated
hence the initialized value is not being used and is redundant. Remove
the initialization. Cleans up clang warning:

warning: Value stored to 'sock' during its initialization is never read

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>