tests: inotify-rotate: avoid race condition with overloaded disk

* tests/tail-2/inotify-rotate: Wait 50% longer for grep to succeed.
Without this change, this test would fail consistently when using
"make -j25 check" with F15 in a virtio- and spinning-rust-backed
virtual machine.

tests/tail-2/inotify-rotate

@@ -24,12 +24,12 @@ fi
 . "${srcdir=.}/init.sh"; path_prepend_ ../src
 expensive_
 
-# Wait up to 10 seconds for grep REGEXP FILE to succeed.
+# Wait several seconds for grep REGEXP FILE to succeed.
 # Usage: grep_timeout REGEXP FILE
 grep_timeout()
 {
     local j
-    for j in $(seq 100); do
+    for j in $(seq 150); do
         grep $1 $2 > /dev/null && return 0
         sleep 0.1
     done