Fix saving and restoring umask

In two cases, we set a different umask for some piece of code and
restore it afterwards.  But if the contained code errors out, the umask
is not restored.  So add TRY/CATCH blocks to fix that.

src/backend/commands/copy.c

@@ -1826,7 +1826,16 @@ BeginCopyTo(ParseState *pstate,
 						 errmsg("relative path not allowed for COPY to file")));
 
 			oumask = umask(S_IWGRP | S_IWOTH);
+			PG_TRY();
+			{
 				cstate->copy_file = AllocateFile(cstate->filename, PG_BINARY_W);
+			}
+			PG_CATCH();
+			{
+				umask(oumask);
+				PG_RE_THROW();
+			}
+			PG_END_TRY();
 			umask(oumask);
 			if (cstate->copy_file == NULL)
 			{

src/backend/libpq/be-fsstubs.c

@@ -538,8 +538,17 @@ be_lo_export(PG_FUNCTION_ARGS)
 	 */
 	text_to_cstring_buffer(filename, fnamebuf, sizeof(fnamebuf));
 	oumask = umask(S_IWGRP | S_IWOTH);
+	PG_TRY();
+	{
 		fd = OpenTransientFile(fnamebuf, O_CREAT | O_WRONLY | O_TRUNC | PG_BINARY,
 							   S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH);
+	}
+	PG_CATCH();
+	{
+		umask(oumask);
+		PG_RE_THROW();
+	}
+	PG_END_TRY();
 	umask(oumask);
 	if (fd < 0)
 		ereport(ERROR,