perf env: Rename some leftovers from rename to perf_env

In ce80d3be ("perf tools: Rename perf_session_env to perf_env") we
forgot to rename a few functions to the "perf_env" prefix, do it now.

Tested-by: Wang Nan <wangnan0@huawei.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-b3ui3z6ock89z1814pu2er98@git.kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>