Renews DHCP lease on suspend

Hi and thanks for pm-graph!

NB: I'm just getting familiar with pm-graph tools, I might be using it wrong

I'm running pm-graph from a git checkout (I didn't make install) on an Intel NUC6i7KYB running Ubuntu Desktop 20.04 and connected to a wired network. I'm running this command over SSH:
sudo ./sleepgraph.py -verbose -m mem -rtcwake 15

I can see the system suspends, resumes and the desktop UI comes back on the graphics output, but shortly after that it renews its DHCP lease and I lose my SSH connection.

This is the console output:
```
lool@rat:~/dev/pm-graph$ sudo ./sleepgraph.py -verbose -m mem -rtcwake 15
Checking this system (rat)...
have root access: YES
is sysfs mounted: YES
is "mem" a valid power mode: YES
is ftrace supported: YES
are kprobes supported: YES
timeline data source: FTRACE (all trace events found)
is rtcwake supported: YES
optional commands this tool may use for info:
turbostat: MISSING
mcelog: MISSING
lspci: FOUND
lsusb: FOUND
netfix: MISSING
os-version : Ubuntu 20.04.6 LTS
baseboard-manufacturer : Intel Corporation
baseboard-product-name : NUC6i7KYB
baseboard-serial-number : BTKY635005R7
baseboard-version : H90766-405
bios-release-date : 03/25/2020
bios-vendor : Intel Corp.
bios-version : KYSKLi70.86A.0067.2020.0325.1553
chassis-manufacturer : Intel Corporation
chassis-version : 1.0
processor-manufacturer : Intel(R) Corporation
processor-version : Intel(R) Core(TM) i7-6770HQ CPU @ 2.60GHz
cpucount : 8
memtotal : 16270972 kB
memfree : 10837720 kB
INITIALIZING FTRACE
Setting trace buffers to 65536 kB (8192 kB per cpu)
INITIALIZING KPROBES
kprobe functions in this kernel:
CPU_OFF: YES
CPU_ON: YES
__pm_notifier_call_chain: NO
acpi_hibernation_begin: YES
acpi_hibernation_enter: YES
acpi_hibernation_leave: YES
acpi_pm_end: YES
acpi_pm_finish: YES
acpi_pm_freeze: YES
acpi_pm_prepare: YES
acpi_pm_thaw: YES
acpi_s2idle_begin: YES
acpi_s2idle_end: YES
acpi_s2idle_prepare: YES
acpi_s2idle_prepare_late: YES
acpi_s2idle_restore: YES
acpi_s2idle_restore_early: YES
acpi_s2idle_sync: NO
acpi_s2idle_wake: YES
acpi_s2idle_wakeup: YES
acpi_suspend_begin: YES
arch_enable_nonboot_cpus_end: NO
async_synchronize_full: YES
create_basic_memory_bitmaps: YES
freeze_kernel_threads: YES
freeze_processes: YES
hibernate_preallocate_memory: YES
ksys_sync: YES
pm_notifier_call_chain: YES
pm_prepare_console: YES
pm_restore_console: YES
pm_restore_gfp_mask: YES
pm_restrict_gfp_mask: YES
resume_console: YES
suspend_console: YES
swsusp_write: YES
sys_sync: NO
syscore_resume: YES
syscore_suspend: YES
thaw_processes: YES
kprobe functions enabled: 36/40
SUSPEND START
will issue an rtcwake in 15 seconds
client_loop: send disconnect: Broken pipe
```

I installed turbostat for completeness, but perhaps this is because I didn't make install and netfix is not in place? There is a brief description of netfix in the help output of sleepgraph that it's to fix the network if suspend fails, but suspend does not seem to fail in my case.

I tried doing a few suspend/resumes manually rather than through sleepgraph, and the system keeps its DHCP lease:
```
sudo rtcwake -s 15
sudo systemctl suspend
```

I'm attaching the results from the latest run:
[suspend-230410-174933.zip](https://github.com/intel/pm-graph/files/11192002/suspend-230410-174933.zip)

Best,
\- LM