HA_BIN backward compatibility

This breaks the backward compatibility with the heartbeat stack.
#285 Low: build: Move binaries in /usr/lib/heartbeat to /usr/libexec/heartbeat to avoid multi-lib inconsistencies

The heatbeat init script expects the heartbeat binary resides in $HA_BIN/heartbeat (/usr/lib64/heartbeat/heatbeat) but it now tries to look /usr/libexec/heartbeat/heartbeat and fails.

Start with the heartbeat init script and compare its use of HA_BIN with the binary locations described in this issue and #285. Trace which path is installed and which path the script checks; done means the heartbeat stack can locate and execute the binary without breaking the intended multi-lib layout.

Written by the indexing model from the issue text.