Alter default for --min-tmpfs

This patch alters the default for the --min-tmpfs flag increasing the
chances of successful image builds in memory restricted environments.

Increasingly, and especially with increasing support for things like
OVB and other virtual deployments, people are deploying underclouds
in somewhat constrained environments.  A regular image build fails
routinely in an undercloud with <= 12GB RAM.  Unfortunately this is
tricky to nail down as the cause since typically the VM undercloud
locks up solid making debugging difficult or impossible.

Increasing this value means image builds complete successfully by
deferring the ramdisk meaning a happier experience for the operator
and negligible difference in the speed of the image creation.

Secondly, this patch adds consistency to flags by standardizing on
the = character.

Change-Id: I8fcd240b7063b4991404e01c08441fe929ff5e69

image-yaml/overcloud-hardened-images.yaml

@@ -37,7 +37,7 @@ disk_images:
       - python-heat-agent-json-file
       - screen
     options:
-      - "--min-tmpfs 5"
+      - "--min-tmpfs=7"
     environment:
       DIB_PYTHON_VERSION: '2'
       DIB_MODPROBE_BLACKLIST: 'usb-storage cramfs freevxfs jffs2 hfs hfsplus squashfs udf vfat bluetooth'

image-yaml/overcloud-images.yaml

@@ -30,7 +30,7 @@ disk_images:
       - device-mapper-multipath
       - openstack-heat-agents
     options:
-      - "--min-tmpfs 5"
+      - "--min-tmpfs=7"
     environment:
       DIB_PYTHON_VERSION: '2'
   -
@@ -50,6 +50,6 @@ disk_images:
     packages:
       - python-hardware-detect
     options:
-      - "--min-tmpfs=5"
+      - "--min-tmpfs=7"
     environment:
       DIB_PYTHON_VERSION: '2'

image-yaml/overcloud-realtime-compute.yaml

@@ -28,7 +28,7 @@ disk_images:
       - device-mapper-multipath
       - openstack-heat-agents
     options:
-      - "--min-tmpfs 5"
+      - "--min-tmpfs=7"
     environment:
       DIB_PYTHON_VERSION: '2'
       DIB_BAREMETAL_KERNEL_PATTERN: 'vmlinuz*.rt*'