Add strict check to VCPUs-params param-key,according to Xen Cloud Platform Administrator's Guide,there's only 'weight','cap' or 'mask' param-key available.
Add strict check to VCPUs-params param-key,according to Xen Cloud Platform Administrator's Guide,there's only 'weight','cap' or 'mask' param-key available.

current:
# xe vm-param-set VCPUs-params:test=33 uuid=b7ca170b-c017-046e-116c-8d4c4d778195
# xe vm-list params=VCPUs-params uuid=b7ca170b-c017-046e-116c-8d4c4d778195
VCPUs-params (MRW)    : test: 33

after patch:
# xe vm-param-set VCPUs-params:test=33 uuid=b7ca170b-c017-046e-116c-8d4c4d778195
Error: Failed to add parameter 'test': expecting 'weight','cap' or 'mask'
# xe vm-list params=VCPUs-params uuid=b7ca170b-c017-046e-116c-8d4c4d778195
VCPUs-params (MRW)    :

Signed-off-by: Yang Hongyang <5089988faad16a34ba6772ee0653fa1817eeab99@cn.fujitsu.com>

jjd27/xen-api,cheng-z/xen-api,cheng--zhang/xen-api,guard163/xen-api,guard163/xen-api,Frezzle/xen-api,ravippandey/xen-api,jjd27/xen-api,huizh/xen-api,huizh/xen-api,cheng-z/xen-api,rafalmiel/xen-api,vasilenkomike/xen-api,thomassa/xen-api,rafalmiel/xen-api,jjd27/xen-api,koushikcgit/xen-api,salvocambria/xen-api,agimofcarmen/xen-api,djs55/xen-api,guard163/xen-api,huizh/xen-api,euanh/xen-api,vasilenkomike/xen-api,srowe/xen-api,cheng-z/xen-api,euanh/xen-api,anoobs/xen-api,robertbreker/xen-api,anoobs/xen-api,salvocambria/xen-api,srowe/xen-api,salvocambria/xen-api,koushikcgit/xen-api,simonjbeaumont/xen-api,cheng-z/xen-api,agimofcarmen/xen-api,euanh/xen-api,anoobs/xen-api,srowe/xen-api,srowe/xen-api,anoobs/xen-api,simonjbeaumont/xen-api,cheng--zhang/xen-api,vasilenkomike/xen-api,robertbreker/xen-api,simonjbeaumont/xen-api,rafalmiel/xen-api,vasilenkomike/xen-api,jjd27/xen-api,djs55/xen-api,anoobs/xen-api,vasilenkomike/xen-api,agimofcarmen/xen-api,koushikcgit/xen-api,cheng--zhang/xen-api,euanh/xen-api,robertbreker/xen-api,simonjbeaumont/xen-api,djs55/xen-api,ravippandey/xen-api,ravippandey/xen-api,djs55/xen-api,thomassa/xen-api,jjd27/xen-api,huizh/xen-api,robertbreker/xen-api,euanh/xen-api,koushikcgit/xen-api,salvocambria/xen-api,salvocambria/xen-api,koushikcgit/xen-api,huizh/xen-api,salvocambria/xen-api,guard163/xen-api,djs55/xen-api,cheng--zhang/xen-api,cheng--zhang/xen-api,thomassa/xen-api,cheng-z/xen-api,vasilenkomike/xen-api,cheng--zhang/xen-api,huizh/xen-api,agimofcarmen/xen-api,anoobs/xen-api,euanh/xen-api,rafalmiel/xen-api,thomassa/xen-api,jjd27/xen-api,simonjbeaumont/xen-api,rafalmiel/xen-api,cheng-z/xen-api,guard163/xen-api,ravippandey/xen-api,simonjbeaumont/xen-api,guard163/xen-api,koushikcgit/xen-api,djs55/xen-api,ravippandey/xen-api,cheng-z/xen-api,thomassa/xen-api,agimofcarmen/xen-api,Frezzle/xen-api,robertbreker/xen-api,rafalmiel/xen-api,agimofcarmen/xen-api,Frezzle/xen-api,srowe/xen-api,ravippandey/xen-api,Frezzle/xen-api,Frezzle/xen-api,cheng--zhang/xen-api,robertbreker/xen-api,thomassa/xen-api