Increase timeout for reimage operation

Looking at the recent failures in the tempest-integrated-compute
job, the reimage operation seems to be taking longer than our
expected time of 60 seconds (which was increased because of a similar
failure in the past, default is 20 seconds).
The main culprit for this failure is the image conversion from qcow2
to raw which is taking ~159 seconds.

Dec 05 13:29:59.709129 np0035951188 cinder-volume[77000]: DEBUG oslo_concurrency.processutils [req-5113eccb-05ba-486a-8130-a58898c8ad35 req-0edf972a-109a-465f-a771-ceb87ecbda3e tempest-ServerActionsV293TestJSON-1780705112 None] CMD "sudo cinder-rootwrap /etc/cinder/rootwrap.conf qemu-img convert -O raw -t none -f qcow2 /opt/stack/data/cinder/conversion/image_download_dbe01f18-1c90-4536-a09a-b49f0811c7a0_copod3cm /dev/mapper/stack--volumes--lvmdriver--1-volume--073a98e8--3c89--4734--9ae5--59af25f8914a" returned: 0 in 159.272s {{(pid=77000) execute /opt/stack/data/venv/lib/python3.10/site-packages/oslo_concurrency/processutils.py:422}}

The recent run took ~165 seconds on the cinder side but it failed
early since the nova operation timed out in 60 seconds hence
deleting the volume.
To be on the safer side, 180 seconds seems to be a sane time for
the operation to complete which this patch configures.

Closes-Bug: 2046252
Change-Id: I8a9628216038f6d363cab5dd8177274c9cfc17c2

lib/nova

@@ -1054,7 +1054,7 @@ function start_nova_compute {
 
     # Set rebuild timeout longer for BFV instances because we likely have
     # slower disk than expected. Default is 20s/GB
-    iniset $NOVA_CPU_CONF DEFAULT reimage_timeout_per_gb 60
+    iniset $NOVA_CPU_CONF DEFAULT reimage_timeout_per_gb 180
 
     # Configure the OVSDB connection for os-vif
     if [ -n "$OVSDB_SERVER_LOCAL_HOST" ]; then