gstrtspconnection: messages_bytes not decreased

The watch->messages_bytes is not decreased when the write operation
from the backlog is only partly successfull.

This commit decreases the watch->messages_bytes for the successfully
sent messages.

Fixes #679
26 jobs for fix-messages_bytes in 140 minutes and 24 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Preparation
passed #771546
gst indent

00:00:30

passed #771545
manifest

00:00:46

 
  Build
passed #771556
build cerbero cross-android universal

00:09:19

manual #771560
gst-ios-12.2 allowed to fail manual
build cerbero cross-ios universal
passed #771557
build cerbero cross win32

00:09:21

passed #771558
build cerbero cross win64

00:04:53

passed #771555
build cerbero fedora x86_64

00:05:52

passed #771559
gst-macos-10.14
build cerbero macos x86_64

00:06:49

passed #771551
build clang fedora x86_64

00:07:39

passed #771547
build fedora x86_64

00:03:11

passed #771554
docker windows 1607
build msys2

00:11:51

passed #771548
build nodebug fedora x86_64

00:05:21

passed #771549
build static fedora x86_64

00:13:56

passed #771550
build static nodebug fedora x86_64

00:03:55

passed #771552
docker windows 1607
build vs2017 amd64

00:10:08

passed #771553
docker windows 1607
build vs2017 x86

00:09:28

 
  Test
failed #771561
check fedora

00:06:28

failed #771562
integration testsuites fedora

02:16:23

passed #771566
valgrind bad

00:11:54

failed #771563
valgrind base

00:18:06

passed #771567
valgrind ges

00:11:49

failed #771564
valgrind good

00:18:55

passed #771565
valgrind ugly

00:02:42

 
  Integrate
passed #771568
cross-android universal examples

00:10:31

skipped #771570
gst-ios-12.2 allowed to fail manual
cross-ios universal examples
passed #771569
documentation

00:04:36

 
Name Stage Failure
failed
integration testsuites fedora Test
           Total: 1447
Uploading artifacts...
gst-build/build/meson-logs/: found 2 matching files
validate-logs: found 70466 matching files

Uploading artifacts to coordinator... ok
id=771562 responseStatus=201 Created token=e_rv75LR
Uploading artifacts...
validate-logs/*.xml: found 1 matching files

Uploading artifacts to coordinator... ok
id=771562 responseStatus=201 Created token=e_rv75LR
ERROR: Job failed: exit code 1
failed
valgrind good Test
           Total: 690
Uploading artifacts...
gst-build/build/meson-logs/: found 2 matching files
validate-logs: found 1478 matching files

Uploading artifacts to coordinator... ok
id=771564 responseStatus=201 Created token=HJ_x_QsA
Uploading artifacts...
validate-logs/*.xml: found 1 matching files

Uploading artifacts to coordinator... ok
id=771564 responseStatus=201 Created token=HJ_x_QsA
ERROR: Job failed: exit code 1
failed
valgrind base Test
           Total: 625
Uploading artifacts...
gst-build/build/meson-logs/: found 2 matching files
validate-logs: found 1324 matching files

Uploading artifacts to coordinator... ok
id=771563 responseStatus=201 Created token=aTqMqk4k
Uploading artifacts...
validate-logs/*.xml: found 1 matching files

Uploading artifacts to coordinator... ok
id=771563 responseStatus=201 Created token=aTqMqk4k
ERROR: Job failed: exit code 1
failed
check fedora Test
           Total: 3151
Uploading artifacts...
gst-build/build/meson-logs/: found 2 matching files
validate-logs: found 3570 matching files

Uploading artifacts to coordinator... ok
id=771561 responseStatus=201 Created token=Lx8vJ5to
Uploading artifacts...
validate-logs/*.xml: found 1 matching files

Uploading artifacts to coordinator... ok
id=771561 responseStatus=201 Created token=Lx8vJ5to
ERROR: Job failed: exit code 1