Added a free statement to release memory allocated for postbuf if the…

Created by: karlvestin

… memory allocation for inbuf fails. Resolves an error level issue generated by the Codacy static code analysis.

Codacy link: https://app.codacy.com/gh/epics-base/epics-base/file/42098735308/issues/source?bid=16430872&fileBranchId=16430872#l201 Launchpad bug: https://bugs.launchpad.net/epics-base/+bug/1862917