[lldb/crashlog] Fix JSON ObjectFile module loading issue

In 27f27d15, we added a new way to use textual (JSON) object files
and symbol files with the interactive crashlog command, using the
inlined symbols from the crash report.

However, there was a missing piece after successfully adding the textual
module to the target, we didn't mark it as available causing the module
loading to exit early.

This patch addresses that issue by marking the module as available when
added successfully to the target.

Differential Revision: https://reviews.llvm.org/D149477



Signed-off-by: Med Ismail Bennani <ismail@bennani.ma>