ceph: remove leading and trailing space from get config
ceph: remove leading and trailing space from get config

Value returned by ceph config get can contains some trailing space which leads to
issues when running other ceph command.
For ex.:
2020-04-06 15:32:43.543050 I | exec: Running command: ceph osd pool set test-1.rgw.control pg_num_min 8
 --connect-timeout=15 --cluster=rook-ceph --conf=/var/lib/rook/rook-ceph/rook-ceph.config --keyring=/var/lib/rook/rook-ceph/client.admin.keyring --format json --out-file /tmp/249563089
2020-04-06 15:32:44.005018 I | exec: Error EINVAL: error parsing int value '8

Signed-off-by: n.fraison <fa178ec1d44ff1d1a89b05327dd758785f1a04d4@criteo.com>

rook/rook,rook/rook,rook/nfs,rook/nfs,rook/rook,rook/nfs,rook/rook,rook/rook