[tests] Increase timeout of fork06 LTP test

Previously, `fork06` LTP test had a default timeout of 30 seconds, which
translated to 60 seconds under AddressSanitizer builds (due to scaling
factor of 2). However, our new Jenkins CI is based on wimpy VMs, and the
default timeout of 60 is not enough for ASan CI jobs anymore.

Signed-off-by: Dmitrii Kuvaiskii <dmitrii.kuvaiskii@intel.com>

libos/test/ltp/ltp.cfg

@@ -551,6 +551,10 @@ skip = yes
 [fork05]
 skip = yes
 
+# performs 1,000 forks, which may be slow on ASan builds and wimpy VMs
+[fork06]
+timeout = 60
+
 # sometimes fails with "x/100 children didn't read correctly from an inheritted fd"
 [fork07]
 skip = yes