TARGET_ROOT is not a valid key during pre-install step. The error
`TARGET_ROOT: unbound variable` raises now.
This PR remove the useless TARGET_ROOT in openeuler-minimal.
Change-Id: I6fae2ca0e6c6e57a3b195367f2626d9e498e0329
The file name under pre-install.d should be like "^[0-9A-Za-z_-]+$",
otherwise the script will be skipped by the name check step and raise
"Ignoring non-conforming filenames" warning.
This patch rename the openeuler mirror script to ensure it follows
the regex.
Change-Id: I6d868df7932345547711100519523546bd53360e