tests: Add getuid() to virnetdevbandwidthmock

When only geteuid() is mocked, the test crashes on Debian 10.

  Fatal: failed to reset uid: No such file or directory

  Program received signal SIGABRT, Aborted.
  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
  50      ../sysdeps/unix/sysv/linux/raise.c: No such file or directory.
  (gdb) t a a bt

  Thread 1 (Thread 0x7ffff3b3e080 (LWP 12003)):
  #0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:50
  #1  0x00007ffff7798535 in __GI_abort () at abort.c:79
  #2  0x00007ffff485ca20 in _gcry_logv (level=level@entry=40, fmt=fmt@entry=0x7ffff4929126 "failed to reset uid: %s\n", arg_ptr=arg_ptr@entry=0x7fffffffe4a0) at ../../src/misc.c:142
  #3  0x00007ffff485cd61 in _gcry_log_fatal (fmt=fmt@entry=0x7ffff4929126 "failed to reset uid: %s\n") at ../../src/misc.c:218
  #4  0x00007ffff48639d1 in lock_pool_pages (n=<optimized out>, p=<optimized out>) at ../../src/secmem.c:340
  #5  _gcry_secmem_init_internal (n=<optimized out>) at ../../src/secmem.c:563
  #6  0x00007ffff4863d78 in _gcry_secmem_init (n=4096) at ../../src/secmem.c:581
  #7  0x00007ffff485e4e6 in _gcry_vcontrol (cmd=<optimized out>, arg_ptr=arg_ptr@entry=0x7fffffffe5e0) at ../../src/global.c:506
  #8  0x00007ffff485a789 in gcry_control (cmd=cmd@entry=GCRYCTL_INIT_SECMEM) at ../../src/visibility.c:79
  #9  0x00007ffff71af10f in ssh_crypto_init () at ./src/libgcrypt.c:621
  #10 0x00007ffff7193796 in _ssh_init (constructor=constructor@entry=1) at ./src/init.c:79
  #11 0x00007ffff71834de in libssh_constructor () at ./src/init.c:116
  #12 0x00007ffff7fe437a in call_init (l=<optimized out>, argc=argc@entry=1, argv=argv@entry=0x7fffffffe778, env=env@entry=0x7fffffffe788) at dl-init.c:72
  #13 0x00007ffff7fe4476 in call_init (env=0x7fffffffe788, argv=0x7fffffffe778, argc=1, l=<optimized out>) at dl-init.c:30
  #14 _dl_init (main_map=0x7ffff7ffe190, argc=1, argv=0x7fffffffe778, env=0x7fffffffe788) at dl-init.c:119
  #15 0x00007ffff7fd60ca in _dl_start_user () from /lib64/ld-linux-x86-64.so.2
  #16 0x0000000000000001 in ?? ()
  #17 0x00007fffffffea26 in ?? ()
  #18 0x0000000000000000 in ?? ()

Signed-off-by: Andrea Bolognani <abologna@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

tests/virnetdevbandwidthmock.c

@@ -24,3 +24,8 @@ uid_t geteuid(void)
 {
     return 0;
 }
+
+uid_t getuid(void)
+{
+    return 0;
+}