Attach to remote pid of one of multiple inferiors fails.

[Asif]

### VERSION:
GNU gdb (GDB) 7.2
This GDB was configured as "--host=x86_64-unknown-linux-gnu
--target=powerpc-linux-gnu".

### MACHINE (HOST):
Linux 2.6.24-28-generic #1 SMP x86_64 GNU/Linux

### MACHINE (TARGET):

### GCC VERSION used to compile gdb:
powerpc-linux-gnu-gcc (GCC) 4.3.2

### GCC VERSION used to compile program being debugged:
powerpc-linux-gnu-gcc (GCC) 4.3.2

### GCC compiler arguments used to compile program being debugged:
-g -O0 -Wl,-Map,powerpc/debug/Map -Wl,--cref

### GDB session log to reproduce the (possible) bug:

NOTE:
1) program1: client using rpc's to communicate (exec remote functions).
2) program2: server accepts rpc's from client (to exec functions).

TARGET:
gdbserver --multi :4444

HOST:
powerpc-linux-gnu-gdb --annotate=3
set sysroot /usr/local/powerpc-linux-gnu-root
set solib-search-path <local-dir-to-unstripped-libs>
directory <local-dir-to-sources>
target extended-remote <TARGET>:4444
file <local-path-to-program2>
add-inferior -exec <local-path-to-program1>
inferior <inferior-id-program2>
set remote exec-file program2
run
detach inferior <inferior-id-program2>
inferior <inferior-id-program1>
set remote exec-file program1
run
detach inferior <inferior-id-program1>
attach <pid-program2>

>>>>>>>>>>>> ERROR MESSAGE (POSSIBLE BUG) <<<<<<<<<<<<
Ignoring packet error, continuing...
Attached to process 1561 <----------------------------- THIS IS
<pid-program2>!!!!
Ignoring packet error, continuing...
Ignoring packet error, continuing...
Ignoring packet error, continuing...
warning: Invalid remote reply: timeout
<<<<<<<<<<<< ERROR MESSAGE (POSSIBLE BUG) >>>>>>>>>>>>

NOTE: Both program1 and program2 on TARGET are still running even
after this ERROR MESSAGE.

--
Asif