mca/base: fix coverity issue

Fixes CID 1357979: Resource leak (RESOURCE_LEAK):

flags array was being leaked. Fixed.

Signed-off-by: Nathan Hjelm <hjelmn@lanl.gov>

opal/mca/base/mca_base_var_enum.c

@@ -514,6 +514,8 @@ static int enum_value_from_string_flag (mca_base_var_enum_t *self, const char *s
         }
     }
 
+    opal_argv_free (flags);
+
     *value_out = flag;
 
     return OPAL_SUCCESS;