Add thread safe environment variables managment functions.
Remove and replace non thread safe custom environment management function.
Replace setenv() function with d_setenv()

Required-githooks: true
Signed-off-by: Cedric Koch-Hofer <cedric.koch-hofer@intel.com>

…/daos-14532-gurt

Required-githooks: true

Integrate reviewers comments:
- Factorize d_getenv_uint() functions.

Required-githooks: true
Signed-off-by: Cedric Koch-Hofer <cedric.koch-hofer@intel.com>

Fix clang format.

Required-githooks: true
Signed-off-by: Cedric Koch-Hofer <cedric.koch-hofer@intel.com>

…/daos-14532-gurt

Required-githooks: true

Integrate reviewers comments:
- Revert d_getenv_XXX interfaces update
- Rename d_free_env() -> d_free_env_str()

Features: mpiio
Required-githooks: true
Signed-off-by: Cedric Koch-Hofer <cedric.koch-hofer@intel.com>

Revert useless header file changes.

Features: mpiio
Required-githooks: true
Signed-off-by: Cedric Koch-Hofer <cedric.koch-hofer@intel.com>

Integrate reviwers comments:
- Checks return code when using standard function calls such as pthread_rwlock_rdlock()

Features: mpiio
Required-githooks: true
Signed-off-by: Cedric Koch-Hofer <cedric.koch-hofer@intel.com>

Fix clang format coding standards.

Features: mpiio
Required-githooks: true
Signed-off-by: Cedric Koch-Hofer <cedric.koch-hofer@intel.com>