Allow multi-line config items in meta-section of local.conf

It would behave such as the contents from each meta-section in
local.conf is copied to the destination files. One exception is the multiline
options not grouped together. In that case, the contents will be grouped
together in its destination config file.

Check tests/test_config.sh for examples.

This was originally committed in https://review.openstack.org/128805.
But the original change used AWK syntax that is not supported in AWK
3.1.8, and caused syntax error on servers with that AWK version. This
patch makes the necessary change so that it's compatible with AWK
3.1.8.

Change-Id: Id1e1fe01f05bd0f19ea6e89c4f4c0f8be695dfce
Partial-Bug: #1374118
Merge "Allow multi-line config items in meta-section of local.conf"