Fix: utils: set env CIB_shadow using os.environ (bsc#1205925)

`os.environ` is captured once from libc on python process startup (when
module `os` is imported from `site.py`) and is the only one interface
able to enumerate environment variables. Changing environment variables
with other interfaces (including `os.putenv`, `os.unsetenv`, or call
libc interface in some CPython modules) makes `os.environ` out of sync
and should be avoided.

crmsh/utils.py

@@ -114,13 +114,14 @@ def this_node():
 
 
 def set_cib_in_use(name):
-    os.putenv(_cib_shadow, name)
+    os.environ[_cib_shadow] = name
     global _cib_in_use
     _cib_in_use = name
 
 
 def clear_cib_in_use():
-    os.unsetenv(_cib_shadow)
+    if _cib_shadow in os.environ:
+        del os.environ[_cib_shadow]
     global _cib_in_use
     _cib_in_use = ''