Stop setting $CARGO_HOME

cargo will use the user's $CARGO_HOME, or $HOME/.cargo by default.

Fixes bug 26497; bugfix on 0.3.1.5-alpha.

src/test/test_rust.sh

@@ -9,7 +9,6 @@ for cargo_toml_dir in "${abs_top_srcdir:-../../..}"/src/rust/*; do
     if [ -e "${cargo_toml_dir}/Cargo.toml" ]; then
 	cd "${cargo_toml_dir}" && \
 	    CARGO_TARGET_DIR="${abs_top_builddir:-../../..}/src/rust/target" \
-	    CARGO_HOME="${abs_top_builddir:-../../..}/src/rust/.cargo" \
 	    "${CARGO:-cargo}" test ${CARGO_ONLINE-"--frozen"} \
 	    ${EXTRA_CARGO_OPTIONS} \
 	    --manifest-path "${cargo_toml_dir}/Cargo.toml" || exitcode=1