Look for the literal string '127.0.0.1', not the regex '127.0.0.1'

In https://buildkite.com/julialang/rr/builds/1638 we saw a test failure due the regex '127.0.0.1' matching 'real_time:25625127.000315'

src/test/tcp_sockets.run

@@ -5,11 +5,11 @@ cp ${OBJDIR}/bin/$exe $exe-$nonce
 just_record $exe-$nonce
 # The test binary might fail due to IPv6 being unsupported
 EXIT_CODE=$?
-if [[ `rr dump --socket-addresses latest-trace|grep --count 127.0.0.1` != 2 ]]; then
+if [[ `rr dump --socket-addresses latest-trace|grep --count -F 127.0.0.1` != 2 ]]; then
     failed "Wrong number of '127.0.0.1's"
 fi
 if [[ $EXIT_CODE == 0 ]]; then
-  if [[ `rr dump --socket-addresses latest-trace|grep --count ::1:` != 2 ]]; then
+  if [[ `rr dump --socket-addresses latest-trace|grep --count -F ::1:` != 2 ]]; then
       failed "Wrong number of '::1:'s"
   fi
-fi
+fi