vstart: make "--crimson" imply "--nodaemon"

If you want to run multiple crimson-osd instances, you need nodaemon. Default
to nodaemon when using crimson.

Add a new "--crimson-foreground" which preserves the old behavior, in case
it's needed.

Signed-off-by: Greg Farnum <gfarnum@redhat.com>

doc/dev/crimson/crimson.rst

@@ -153,7 +153,7 @@ So, a typical command to start a single-crimson-node cluster is::
 
   $  MGR=1 MON=1 OSD=1 MDS=0 RGW=0 ../src/vstart.sh -n -x \
     --without-dashboard --cyanstore \
-    --crimson --nodaemon --redirect-output \
+    --crimson --redirect-output \
     --osd-args "--memory 4G"
 
 Where we assign 4 GiB memory, a single thread running on core-0 to crimson-osd.

src/vstart.sh

@@ -233,6 +233,7 @@ options:
 	--msgr2: use msgr2 only
 	--msgr21: use msgr2 and msgr1
 	--crimson: use crimson-osd instead of ceph-osd
+    --crimson-foreground: use crimson-osd, but run it in the foreground
 	--osd-args: specify any extra osd specific options
 	--bluestore-devs: comma-separated list of blockdevs to use for bluestore
 	--bluestore-zoned: blockdevs listed by --bluestore-devs are zoned devices (HM-SMR HDD or ZNS SSD)
@@ -301,6 +302,11 @@ case $1 in
         ;;
     --crimson)
         ceph_osd=crimson-osd
+        nodaemon=1
+        ;;
+    --crimson-foreground)
+        ceph_osd=crimson-osd
+        nodaemon=0
         ;;
     --osd-args)
         extra_osd_args="$2"