valgrind: Adjust suppressions to handle glibc changes

In newer glibc versions two additional functions appear between
send() and socketcall.send(msg):
   fun:__internal_syscall_cancel
   fun:__syscall_cancel
Due to that our existing suppression do not work anymore.

Use '...', like aleady used in other suppressions, to make valgrind ignore
these interstitial frames.

The problematic suppressions are only in < 15, as they aren't needed after
5891c7a8ed.

Discussion: https://postgr.es/m/d7pyc6wbo2rqhfk24lsgz37766n75vty4jxy5dnppny7ezd4qc@56juadvntebw
Backpatch-through: 13

src/tools/valgrind.supp

@@ -19,6 +19,7 @@
 	Memcheck:Param
 	socketcall.send(msg)
 
+	...
 	fun:*send*
 	fun:pgstat_send
 }
@@ -28,6 +29,7 @@
 	Memcheck:Param
 	socketcall.sendto(msg)
 
+	...
 	fun:*send*
 	fun:pgstat_send
 }