[gdb/testsuite] Fix timeout in gdb.fortran/info-types.exp

[gdb/testsuite] Fix timeout in gdb.fortran/info-types.exp

When running the testsuite in an enviroment that simulates a stressed system,
I ran into a timeout in test-case gdb.fortran/info-types.exp:
...
(gdb) info types^M
FAIL: gdb.fortran/info-types.exp: info types (timeout)
...

This is mainly due the presence of glibc debug info.

With it installed, I get:
...
$ time gdb -q -batch -x outputs/gdb.fortran/info-types/gdb.in.1 > /dev/null
real	0m35.969s
user	0m38.231s
sys	0m1.007s
...
and without:
...
$ time gdb -q -batch -x outputs/gdb.fortran/info-types/gdb.in.1 > /dev/null
real	0m4.782s
user	0m5.014s
sys	0m0.304s
...

Fix this by not running to main, which gets us:
...
$ time gdb -q -batch -x outputs/gdb.fortran/info-types/gdb.in.1 > /dev/null
real	0m0.808s
user	0m0.789s
sys	0m0.137s
...

Likewise in gdb.mi/mi-sym-info.exp and gdb.mi/mi-complete.exp.

Tested on x86_64-linux.

Approved-By: Tom Tromey <tom@tromey.com>