test: split out host_has_{btrfs,mdadm}() from TEST-64-UDEV-STORAGE

test/TEST-64-UDEV-STORAGE/test.sh

@@ -24,7 +24,7 @@ _host_has_feature() {(
 
     case "${1:?}" in
         btrfs)
-            modprobe -nv btrfs && command -v mkfs.btrfs && command -v btrfs || return $?
+            host_has_btrfs
             ;;
         iscsi)
             # Client/initiator (Open-iSCSI)
@@ -36,7 +36,7 @@ _host_has_feature() {(
             command -v lvm || return $?
             ;;
         mdadm)
-            command -v mdadm || return $?
+            host_has_mdadm
             ;;
         multipath)
             command -v multipath && command -v multipathd || return $?

test/test-functions

@@ -1190,6 +1190,11 @@ install_lvm() {
     mkdir -p "${initdir:?}/etc/lvm"
 }
 
+host_has_btrfs() (
+    set -e
+    modprobe -nv btrfs && command -v mkfs.btrfs && command -v btrfs || return $?
+)
+
 install_btrfs() {
     instmods btrfs
     # Not all utilities provided by btrfs-progs are listed here; extend the list
@@ -1257,6 +1262,11 @@ install_iscsi() {
     fi
 }
 
+host_has_mdadm() (
+    set -e
+    command -v mdadm || return $?
+)
+
 install_mdadm() {
     local unit
     local mdadm_units=(