Fix gh#7747 - filter bare newline output and log client pull to stdout

Docker-DCO-1.1-Signed-off-by: Phil Estes <estesp@linux.vnet.ibm.com> (github: estesp)
pkg/jsonlog: avoid JSONLog allocation in loop

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
daemon/logs: lower allocations in loop

Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
Merge pull request #8109 from unclejack/avoid_jsonlog_alloc

daemon/logs: avoid JSONLog struct alloc in loop
Merge pull request #7942 from estesp/7747-stderr-stdout-bug

Fix gh#7747: filter bare newline output and log client pull to stdout