Previously, run-cli-tests ignored all environment variables from the parent
process to ensure a clean test environment. However, this also dropped
sanitizer settings (ASAN_OPTIONS and LSAN_OPTIONS) needed when AddressSanitizer
is enabled.

This causes test failures with TCMalloc due to false-positive leak reports
from TCMalloc's internal objects, which is a known issue documented in
Google's C++ style guide. While recent gperftools releases have fixed this,
Ubuntu Jammy still ships with an older version that triggers these warnings.

This change preserves sanitizer environment variables while maintaining
the clean test environment for other variables.

Note: Once we upgrade to newer gperftools, we can remove the related
suppression rule in qa/lsan.supp.

The test failure with TCMalloc looks like:

```
/home/jenkins-build/build/workspace/ceph-pull-requests/src/test/cli/ceph-kvstore-tool/help.t: failed
--- /home/jenkins-build/build/workspace/ceph-pull-requests/src/test/cli/ceph-kvstore-tool/help.t
+++ /home/jenkins-build/build/workspace/ceph-pull-requests/src/test/cli/ceph-kvstore-tool/help.t.err
@@ -21,3 +21,19 @@
     stats
     histogram [prefix]

+
+  =================================================================
+  ==87908==ERROR: LeakSanitizer: detected memory leaks
+
+  Direct leak of 45 byte(s) in 1 object(s) allocated from:
+      #0 0x562fd797265d in operator new(unsigned long) (/home/jenkins-build/build/workspace/ceph-pull-requests/build/bin/ceph-kvstore-tool+0xe5e65d) (BuildId: 7eb56077b615aeb3c7aedafa0818ad89fdf3702d)
+      #1 0x562fd79815c8 in std::__new_allocator<char>::allocate(unsigned long, void const*) /usr/lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/new_allocator.h:137:27
+      #2 0x562fd7981520 in std::allocator<char>::allocate(unsigned long) /usr/lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/allocator.h:188:32
+      #3 0x562fd7981520 in std::allocator_traits<std::allocator<char>>::allocate(std::allocator<char>&, unsigned long) /usr/lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/alloc_traits.h:464:20
+      #4 0x562fd798115a in std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>::_M_create(unsigned long&, unsigned long) /usr/lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/basic_string.tcc:155:14
+      #5 0x562fd798787f in std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>::_M_mutate(unsigned long, unsigned long, char const*, unsigned long) /usr/lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/basic_string.tcc:328:21
+      #6 0x562fd79876a7 in std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char>>::_M_append(char const*, unsigned long) /usr/lib/gcc/x86_64-linux-gnu/12/../../../../include/c++/12/bits/basic_string.tcc:420:8
+      #7 0x7fa1aa0286f0 in MallocExtension::Initialize() (/lib/x86_64-linux-gnu/libtcmalloc.so.4+0x2a6f0) (BuildId: eeef3d1257388a806e122398dbce3157ee568ef4)
+
+  SUMMARY: AddressSanitizer: 45 byte(s) leaked in 1 allocation(s).
```

Signed-off-by: Kefu Chai <tchaikov@gmail.com>