Fix memory leaks in mdmfs

[trix_juniper.net]

Summary

mdmfs.c main : the local variable mdconfig_arg is allocated but never freed.

mdmfs.c do_mdconfig_attach_au : the local variable linebuf is allocated but never freed.

In both cases, free the memory after its last use.

Test Plan

Run clang static analyzer, scan-build, before to reproduce the problem. Run after to verify problem resolution.

[ak]

Shouldn't you also free newfs_arg and mount_arg ?

[trix_juniper.net]

I agree these should also be freed.
I took a second look at the scan-view output and it did not complain which is troubling.