The boot release file name for this subsystem, with extension '.rel'.
If a file name is specified (a non-zero-length string), then this
release file takes precedence over the system-wide boot release file
(juniSystemBootReleaseFile) just for modules of the type specified by
the subsystem name. On a set operation, if there is no file that
matches the name specified, then an inconsistentValue error will be
returned. Setting this object to a zero-length string deconfigures the
subsystem-specific backup release file.