Log messages from dpdk library overflow and is written as multiple lines causing issues for testsuite

[Frode Nordahl]

The Open vSwitch system testsuites make assertions based on contents of the ovs-vswitchd.log file.

While attempting to enable the DPDK system tests as part of the autopkgtests, we found that currently the log messages from DPDK overflow and are written out across multiple lines.

I find nothing obvious in OVS that causes this, so I wonder if this is an issue in DPDK, how we build/relate it in Ubuntu or if OVS needs to initialize it differently.

Example log excerpts:
Log line:
2023-05-09T14:48:05.958Z|00063|dpdk|INFO|VHOST_CONFIG: (/tmp/autopkgtest.FzfwzO/autopkgtest_tmp/o/src/_debian/tests/system-dpdk-testsuite.dir/07/dpdkvhostclient0) vhost-
2023-05-09T14:48:05.958Z|00064|dpdk|INFO|user client: socket created, fd: 116

Assertion:
../../tests/system-dpdk.at:335: grep "VHOST_CONFIG: ($OVS_RUNDIR/dpdkvhostclient0) vhost-user client: socket created" ovs-vswitchd.log
stdout:
../../tests/system-dpdk.at:335: exit code was 1, expected 0

Log line:
2023-05-09T16:51:15.505Z|00066|dpdk|WARN|VHOST_CONFIG: (/tmp/nqQypV/_debian/tests/system-dpdk-testsuite.dir/03/dpdkvhostclient0) failed to connect: No such file or direc
2023-05-09T16:51:15.505Z|00067|dpdk|WARN|tory