logs: adjust handling around partial log messages

In libpod/logs.LogLine.Write(), don't write a newline to stdout/stderr
when the log message is only part of a line.

In libpod.ConmonOCIRuntime.HTTPAttach(), don't send a newline over the
HTTP connection when the log message is only part of a line.

In pkg/api/handlers/compat.LogsFromContainer(), don't send a newline
over the HTTP connection when the log message is only part of a line,
and don't make doing so conditional on whether or not the client used
the docker or podman endpoint.

In pkg/domain/infra/tunnel.ContainerEngine.ContainerLogs(), don't add
our own newline to log messages, since they already come through from
the server when they need to.

Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>

libpod/oci_conmon_linux.go

@@ -625,9 +625,11 @@ func (r *ConmonOCIRuntime) HTTPAttach(ctr *Container, req *http.Request, w http.
 				if err != nil {
 					break
 				}
-				_, err = httpBuf.Write([]byte("\n"))
-				if err != nil {
-					break
+				if !logLine.Partial() {
+					_, err = httpBuf.Write([]byte("\n"))
+					if err != nil {
+						break
+					}
 				}
 				err = httpBuf.Flush()
 				if err != nil {