ingest/ledgerbackend: Place history section at the end of the captive core config file

[tamirms]

PR Checklist

PR Structure

• This PR has reasonably narrow scope (if not, break it down into smaller PRs).
• This PR avoids mixing refactoring changes with feature changes (split into two PRs
  otherwise).
• This PR's title starts with name of package that is most changed in the PR, ex.
  services/friendbot, or all or doc if the changes are broad or impact many
  packages.

Thoroughness

• This PR adds tests for the most critical parts of the new functionality or fixes.
• I've updated any docs (developer docs, .md
  files, etc... affected by this change). Take a look in the docs folder for a given service,
  like this one.

Release planning

• I've updated the relevant CHANGELOG (here for Horizon) if
  needed with deprecations, added features, breaking changes, and DB schema changes.
• I've decided if this PR requires a new major/minor version according to
  semver, or if it's mainly a patch change. The PR is targeted at the next
  release branch if it's not a patch change.

What

When using a captive core append file consisting of:

PEER_PORT=11725

UNSAFE_QUORUM=true
FAILURE_SAFETY=0

[[VALIDATORS]]
NAME="local_core"
HOME_DOMAIN="core.local"
# From "SACJC372QBSSKJYTV5A7LWT4NXWHTQO6GHG4QDAVC2XDPX6CNNXFZ4JK"
PUBLIC_KEY="GD5KD2KEZJIGTC63IGW6UMUSMVUVG5IHG64HUTFWCHVZH2N2IBOQN7PS"
ADDRESS="localhost"
QUALITY="MEDIUM"

Captive core crashes with the following error:

ERRO[2020-12-08T10:13:56.544+01:00] default: Got an exception: Failed to parse '/var/folders/kp/q0h17t117h98gz5lf4cqtylm0000gp/T/captive-stellar-core-4b1cf0c8a1267703/stellar-core.conf' :Unknown HISTORY-table entry: 'FAILURE_SAFETY', within [HISTORY.h0] [CommandLine.cpp:1064]  pid=55182 service=ingest subservice=stellar-core

To fix this, I moved the history section at the end of the generated captive core configuration file.

Known limitations

[N/A]

[2opremio]

With this change, append is not append anymore :S

[tamirms]

With this change, append is not append anymore :S

this is true but I'm reluctant to change the name from ConfigAppendPath after we spent so much time discussing the name in the previous PR 😅