ts: clear MODULES_QUARANTINE_SUPPORT prior tests

Author: xdelaruelle

testsuite/install.00-init/010-environ.exp

@@ -46,6 +46,7 @@ catch {unset env(__MODULES_LMVARIANT)}
 catch {unset env(__MODULES_LMINIT)}
 
 catch {unset env(MODULES_RUN_QUARANTINE)}
+unsetenv_var MODULES_QUARANTINE_SUPPORT
 
 foreach var [array names env] {
    if {[string match __MODULES_SHARE_* $var] \

testsuite/modules.00-init/010-environ.exp

@@ -49,6 +49,7 @@ catch {unset env(__MODULES_LMINIT)}
 catch {unset env(MODULECONTACT)}
 
 catch {unset env(MODULES_RUN_QUARANTINE)}
+unsetenv_var MODULES_QUARANTINE_SUPPORT
 
 foreach var [array names env] {
     if {[string match __MODULES_SHARE_* $var] \