replace tabs with spaces in various files

The affected files in this patch had inconsistent use of tabs vs. spaces
for indentation, and this patch eliminates the stray tabs.

Also, the opening brace of sigchld_hdl() in activate.c was moved so the
opening braces are consistent throughout the file.

src/core/execute.c

@@ -1727,10 +1727,10 @@ int exec_context_load_environment(const ExecContext *c, char ***l) {
 
                                 strv_free(r);
                                 return k;
-                         }
+                        }
                         /* Log invalid environment variables with filename */
-			if (p)
-	                        p = strv_env_clean_log(p, pglob.gl_pathv[n]);
+                        if (p)
+                                p = strv_env_clean_log(p, pglob.gl_pathv[n]);
 
                         if (r == NULL)
                                 r = p;